Tart, rosy-red rhubarb is cooked down to a silky jam and sandwiched between buttery layers of shortbread crust on the bottom and brown sugar crumbles on top, to make these decadent, pastry-like Rhubarb Crumble Bars. But why stop there? “Drizzle” is a bit of an understatement for the amount of white chocolate poured on top of these bars. Jackson Pollack would approve.
White chocolate is extremely sweet, and it needs something tart and fruity to temper that sweetness. The rhubarb in these bars takes care of that handily. I’ve added just enough sugar to the rhubarb to help it set into a jam, but it’s still sour enough to make your mouth pucker if you sneak a taste of the filling before the bars are assembled and baked. The final result is an exciting play of sweet and sour, crumbly and soft on your tongue, with the thick creaminess of the white chocolate as the finishing touch.
Seek out the reddest rhubarb you can find, for the prettiest color in the filling. I have rhubarb growing in my garden right now, but the stalks are skinny and very green, so I went to a farm stand and found just what I was looking for.
It only takes a few minutes in the skillet to break the rhubarb down to a chunky compote. Keep cooking until the mixture is very thick, with no evidence of runny syrup remaining. You don’t want excess moisture in the rhubarb to make the bars soggy.
Many recipes for crumble bars call for making one dough and using it for both the bottom crust and the crumble on top. Both layers are made of flour, butter, sugar and salt, so why not? It’s true that they have the same ingredients, but in these Rhubarb Crumble Bars the two layers have different textures so the proportions of the ingredients, and the technique for mixing them, are different. The sugar in the crust is white/granulated (for crispness) and the butter is soft, to blend with the sugar in a cookie-like dough. The sugar in the topping is brown (for depth of flavor) and the butter is cold, to blend with the flour in a pastry-like dough. Yes, it’s an extra step to make each one separately, but it only adds a couple of minutes to the preparation time, and you don’t even have to wash the bowl in between. The results are worth it – you’ll see.
And maybe you’ve noticed what’s missing from this crumble? No oats, no nuts. Don’t be tempted to add either of those – they’re not necessary and will just throw off the balance of flavors and textures.
These bars are delicate, best eaten on a plate with a fork rather than out of hand like some other bars. In fact they don’t have to be bars at all. Bake them in a tart pan (9 inches round and 1 inch deep), and cut wedges instead of squares for a rhubarb tart if you prefer.
Making these ahead and what to do with leftovers:
- Rhubarb Crumble Bars are at their absolute buttery crumbly best the day they’re baked, so make them the day of serving if you’re planning a special meal for a date night or for friends.
- That said, leftovers are fantastic and hold up very well if stored properly. Store leftover bars in the refrigerator, in a single layer in an airtight container, for up to 3 days.
- For longer storage, freeze the bars. To freeze, arrange the cut bars on a baking sheet lined with wax paper and freeze them unwrapped until frozen solid (overnight is fine), then wrap individually in plastic wrap, then transfer to a freezer-safe zip-lock bag. Freeze for up to a month. Thaw for a couple of hours at cool room temperature, or overnight in the refrigerator.
To see these bars combined with other recipes in a springtime menu, read the post for Saturday May 16, 2020.
Rhubarb Crumble Bars with White Chocolate Drizzle
Ingredients
- For the filling:
- 1 pound of trimmed rhubarb, cut into 1-inch pieces (about 4 cups)
- ¼ cup granulated sugar
- 2 tablespoons Grand Marnier, or orange juice
- For the crust:
- 1 2/3 cup (7 1/8 ounces or 200 grams) all-purpose flour
- ¼ teaspoon Diamond Crystal kosher salt (or 1/8 teaspoon Morton’s)
- 12 tablespoons (6 ounces or 1½ sticks) unsalted butter, preferably European style, at room temperature
- ½ cup granulated sugar
- 1 teaspoon pure vanilla extract
- For the topping:
- ½ cup plus 1 tablespoon (2 3/8 ounces or 68 grams) all-purpose flour
- 1/3 cup brown sugar
- Pinch of kosher salt
- 4 tablespoons (2 ounces or ½ stick) cold unsalted butter, preferably European style
- 3 ounces white chocolate
Directions
- Step 1 Toss the rhubarb with ¼ cup of the granulated sugar and the Grand Marnier (or orange juice) in a medium skillet and place the skillet over medium heat. Once the mixture starts to simmer, cover the skillet. Cook, covered, stirring occasionally, until the rhubarb has softened and broken down, 10 to 12 minutes. Remove the lid, raise the heat to medium-high. Cook, stirring frequently to make sure the mixture doesn’t stick to the skillet, until it thickens to a jammy consistency with no runny syrup remaining, 3 to 5 minutes. Transfer the mixture to a bowl and set it aside to cool to room temperature. If you want to you can hasten this process by carefully placing the bowl with the rhubarb mixture into a larger bowl that’s half full of ice water. Be careful that the level of ice water isn’t high enough to slop into the rhubarb. Stir the rhubarb occasionally to speed the cooling.
- Step 2 Heat the oven to 350 degrees. Cut two sheets of parchment paper, each 9 inches wide. Lay the parchment sheets in a 9-inch square baking pan, perpendicular to each other so the ends of the paper extend out all four sides to make handles, to be used later for removing the bars from the pan.
- Step 3 Make the crust. In a small bowl, toss together 1 2/3 cups of flour with ¼ teaspoon of kosher salt if using Diamond Crystal, or 1/8 teaspoon of Morton’s.
- Step 4 In the bowl of a stand mixer, combine the 12 tablespoons of softened butter with ½ cup of granulated sugar. Beat on medium speed for 2 minutes until the mixture is light and fluffy. Scrape down the bowl, the beat in the vanilla. Add the flour/salt mixture and beat on low speed, then gradually increase the speed to medium and beat just until the dough comes together.
- Step 5 Transfer the dough to the prepared pan. Spread it out and pat it into a crust, pushing the dough up the sides all around the edges of the pan to form about a ½-inch raised edge. Set the crust aside.
- Step 6 Make the crumble topping. In the same mixing bowl (no need to clean it out in between), combine ½ cup plus 1 tablespoon of flour with the brown sugar and a pinch of kosher salt, and beat on low to mix them together. Use your fingers to rub and break up any large balls of brown sugar. Cut the 4 tablespoons of chilled butter into ½-inch cubes and add them to the mixture. Start the mixer on the lowest speed, then gradually increase the speed to medium and beat just until most pieces of the butter are broken down to the size of peas. Remove the bowl from the mixer and use your fingers to rub the butter into the mixture and incorporate any remaining larger pieces.
- Step 7 Spread the cooled rhubarb filling over the crust, inside the well formed by the raised edge. Sprinkle the crumble topping over the rhubarb.
- Step 8 Bake the bars for 50 to 55 minutes, until the rhubarb is bubbling and the edges of the crust and the top of the crumble are light golden brown. Remove the pan to a baking rack to cool completely.
- Step 9 Chop the white chocolate and transfer it to a small microwave-safe bowl. Heat the white chocolate in the microwave on medium power for 2 minutes. Stir, then microwave for a few seconds more and stir again until all of the white chocolate is melted and smooth.
- Step 10 Carefully lift the bars out of the pan using the parchment handles and transfer the block to a cutting board. Cut the block into 9 square bars. Place the bars on a baking sheet lined with parchment. Working quickly while the chocolate is warm, use a spoon to drizzle the white chocolate over the bars, as neatly or messily as you like. Let them sit until the chocolate is set before serving.
