For the crust:
1/2 c. chopped almonds
1 c. flour
1/2 c. sugar
1/8 tsp. salt
3/4 c. butter (frozen and cut into 10 pieces)
1 1/2 Tbsp. white wine vinegar
For the filling:
3 Tbsp. flour
1/2 c. sugar
1/2 tsp. cinnamon
1/8 tsp. ginger
1/4 tsp. nutmeg
2 Tbsp. butter, cut into pea-size pieces
2 1/2 c. blueberries
2 1/2 c. raspberries
For the topping:
1 c. blueberries
1 c. raspberries
To prepare the crust, start by placing the almonds in the bowl of a food processor fitted with a metal blade. Pulse the food processor on and off just until the almonds take on the texture of coarse meal. Add the flour, sugar, and salt pulse briefly to combine.
Add the butter pieces to the bowl of the food processor. Pulse the processor on and off until the butter is cut in and the mixture again resembles coarse meal. Do not overwork the dough or it will become tough. Some streaks of butter may remain.
Pour in the vinegar and pulse to incorporate it into the dough. Check the texture of the dough. It should hold together when pinched between two fingers. Add a touch more vinegar if it is too dry, pulsing again to combine. The dough should remain crumbly; it should not feel wet or sticky.
Pour the crumbled dough into a 9-in. springform pan. Pat it into place across the bottom of the pan and up the side walls to a height of 1 in. Refrigerate the crust until ready to use.
To prepare the filling, combine the flour, sugar and spices in a large bowl. Add the butter to the flour mixture and then the berries. Using a rubber spatula, toss gently until the berries are well-coated.
Preheat the oven to 400°F/205°C.
Pour the filling into the crust, distributing the berries evenly across the bottom of the pan. Bake the tart for 50 - 60 minutes or until the crust is golden and filling is bubbly.
Cool the tart in the springform pan for 1 hour before releasing its sides.
Arrange the topping ingredients in a single, decorative layer over the cooked filling. Serve with a dollop of crème fraiche, ice cream or freshly whipped cream.