From America's Test Kitchen Season 1: Crisps, Cobblers, and Gratins
There is seldom anything crisp about most crisps. This simple fruit dessert usually comes out of the oven with a soggy, mushy topping—quite a letdown from the ideal of a warm, fruity filling covered in a crunchy, sweet topping. We set out to make peach crisp that wouldn’t disappoint, one with the perfect balance of nicely thickened filling and a lightly sweetened, crisp topping. We tried everything from Grape-Nuts to cookie crumbs and found the ideal topping mixture to be chopped nuts, butter, and flour. Cutting the butter into the flour is crucial for creating a crisp topping, and we found that a food processor was ideally suited to producing a mixture that resembles crumbly wet sand. Another issue to tackle was sugar: what kind and how much. White sugar alone was too bland, while brown sugar on its own was too strong tasting. A 50-50 mix of the two proved to be the perfect combination. We decided not to use too much sugar in the fruit filling so there would be some contrast with the topping. And we nixed the idea of a thickener—the filling without one had a nicely bright fresh fruit flavor and the topping remained crisp whether we used one or not.
To make a larger crisp that serves 10, double all the ingredients, use a 13 x 9-inch baking pan, and bake for 55 minutes at 375 degrees, without increasing the oven temperature. If making an apple crisp, we recommend equal quantities of Granny Smith and McIntosh apples. Peel, core, and cut apples and pears into one-inch chunks. Peel, pit, and cut nectarines, peaches, and plums into half-inch wedges. If using plums, add one tablespoon quick-cooking tapioca to the fruit mixture. Half a teaspoon of grated fresh ginger makes a nice flavor addition to all the fruits.