PREHEAT THE OVEN

Thirty minutes or longer before baking, set an oven rack in the lower third of the oven. Set the oven at 400ºF/200ºC if using a Pyrex baking dish, at 425ºF/220ºC if using some other dish.

MISE EN PLACE

1. Thirty minutes to 1 hour ahead, cut the butter into 4 pieces and set it on the counter at room temperature (65º to 75ºF/19º to 24ºC).
2. With dish washing liquid, wash the lemons. Rinse, dry, and zest them for both the topping and filling.

MAKE THE CRUMB TOPPING:

FOOD PROCESSOR METHOD

1. In a food processor, pulse together the lemon zest, sugar, rolled oats, and salt until well combined.
2. Add the flour, butter, and vanilla and pulse until the mixture is coarse and crumbly.
3. Empty the crumb topping into a small bowl and, with your fingertips, lightly work the mixture until it starts to clump together.

HANDHELD MIXER METHOD

1. In a medium bowl, mix the butter, sugar, vanilla, and lemon zest on medium speed until smooth and creamy.
2. In a medium bowl, whisk together the flour, rolled oats, and salt.
3. Add the flour mixture to the butter mixture and mix on low speed just until incorporated.
4. Remove the bowl from the stand and, with your fingertips, lightly work the mixture until it starts to clump together.

MAKE THE BERRY FILLING:

1. In a large bowl, stir together the sugar, cornstarch, salt, and lemon zest.
2. Add the raspberries and blueberries and toss to coat them. Sprinkle with the lemon juice and, with a silicone spatula, gently mix the berries until the sugar is moistened. Allow to sit for 10 to 15 minutes for the berries to exude some of their juices.
3. Transfer the berry mixture to the baking dish.

APPLY THE CRUMB TOPPING

Sprinkle the crumb topping evenly over the filling.

BAKE THE CRISP

Bake for 30 to 40 minutes, or until the topping is crisp and golden brown and the juices beneath are bubbling thickly.

COOL THE CRISP

Set the baking dish on a wire rack and let the crisp cool for at least 20 min­utes. Serve the crisp warm or at room temperature, preferably with a scoop of ice cream slowly melting on top.

STORE: Best eaten soon after baking. If necessary, store uncovered, refrigerated, for 1 day.

Make This Recipe Your Own: I like to serve this crisp with vanilla ice cream. Lemon and raspberry also go well with it.

Excerpted from Rose’s Baking Basics © 2018 by Rose Levy Beranbaum. Photography © 2018 by Matthew Septimus. Reproduced by permission of Houghton Mifflin Harcourt. All rights reserved.