¼ cup each almonds, pecans, and hazelnuts
¾ cup whole-wheat flour
¼ cup sugar
¼ teaspoon sea salt
6 tablespoons chilled butter, diced
1 large egg yolk
½ cup sour cream
½ cup plain Greek yogurt
2 tablespoons light brown sugar
1 teaspoon vanilla extract
¼ teaspoon grated orange zest
1 cup blueberries
1 cup raspberries
1 tablespoon orange juice
To make Crust: Preheat oven to 350°F. Coat 9-inch tart pan with cooking spray. Spread nuts on baking sheet, and toast in oven 12 to 15 minutes, or until browned.
Pulse nuts, flour, sugar, and salt in food processor until nuts are ground to powder. Add butter, and pulse until mixture resembles coarse meal. Add egg yolk, and pulse until moist clumps form. Press dough into bottom and sides of prepared pan, about 1/4-inch thick, and pierce with fork. Freeze 30 minutes.
Adjust oven temperature to 400°F. Bake Crust 12 to 14 minutes, or until golden. Cool.
To make Filling: whisk together sour cream, yogurt, brown sugar, vanilla, and orange zest in small bowl. Toss berries with orange juice in separate bowl.
Spread sour cream mixture in crust with spatula. Spoon berries over top a little at a time, until sour cream mixture is evenly covered. Refrigerate 30 to 60 minutes before serving.