Topping:

1 cup all purpose flour

6 tablespoons (packed) golden brown sugar

1 teaspoon finely grated lemon peel

1/2 teaspoon salt

1/2 cup (1 stick) unsalted butter, melted

1 teaspoon vanilla extract

Filling:

2 large eggs

1 cup crème fraîche or sour cream

1 teaspoon vanilla extract

1 tablespoon plus 1/2 cup all purpose flour

½ pint blackberries (two 5.6- to 6-ounce packages)

4 medium peaches (about 18 ounces total), pitted, cut into 11/2-inch cubes

1/4 cup sugar

For topping: 
Whisk flour, golden brown sugar, lemon peel, and salt in medium bowl to blend. Add melted butter and vanilla; stir until evenly moistened but crumbly. DO AHEAD: Can be made 4 hours ahead. Let stand at room temperature.

For filling:
Whisk eggs in large bowl to blend. Whisk in crème fraîche and vanilla. Add 1 tablespoon flour; whisk to blend. do ahead Can be made 4 hours ahead. Cover and chill. Whisk again before continuing.

Preheat oven to 375°F. Butter 8×10- inch oval ceramic dish. Place berries and peaches in large bowl. Sprinkle remaining 1/2 cup flour and sugar over; toss to coat. Transfer to prepared dish. Pour egg mixture evenly over fruit. Using fingers, crumble topping over fruit, distributing evenly.

Bake crisp until custard is set and topping is golden brown, about 55 minutes. Let cool at least 10 minutes and up to 1 hour before serving.