For the shortbread:
- 12 Tbs. (1 1/2 sticks) chilled unsalted butter,
cut into 1-inch pieces
- 2 cups all-purpose flour
- 1/2 cup ground toasted almonds
- 1/2 cup granulated sugar
- 1/2 tsp. salt
For the blackberry curd:
- 2 pints blackberries
- 4 eggs
- 1 1/2 cups granulated sugar
- Pinch of salt
- 1 Tbs. fresh lemon juice
- 4 Tbs. (1/2 stick) unsalted butter, at room
temperature, cut into 1-inch pieces
Confectioners' sugar for dusting
To make the shortbread, in the bowl of a food processor, combine the butter, flour, almonds, granulated sugar and salt and process until small lumps form. Sprinkle the mixture into the prepared pan and press evenly into the bottom. Bake until the shortbread is golden, about 20 minutes. Transfer the pan to a wire rack. Reduce the oven temperature to 325°F.
Meanwhile, make the blackberry curd: In a food processor or blender, puree the blackberries until smooth. Pass the puree through a chinois set over a bowl, using a pestle to press on the solids and extract as much juice as possible; discard the solids. You should have about 3/4 cup juice.
In the top pan of a double boiler or in a nonreactive saucepan, whisk together the eggs and granulated sugar until blended. Then whisk in the blackberry juice, salt and lemon juice. Set the top pan over but not touching simmering water in the bottom pan, or set the saucepan over medium-low heat. (If using a saucepan, take care not to heat the mixture too quickly.) Cook, stirring constantly with a wooden spatula or spoon, until the mixture is warmed through, 1 to 2 minutes.
Begin adding the butter a little at a time, stirring each addition until blended before adding more. Continue cooking, stirring constantly and scraping the bottom of the pan, until a finger drawn across the back of the spatula leaves a path, 8 to 10 minutes more. Immediately remove the pan from the heat. Pass the curd through the chinois set over a bowl and let stand for 10 minutes. Whisk to blend, then pour the curd over the shortbread, spreading it evenly to the edges.
Bake until the curd is set, about 30 minutes. Transfer the pan to a wire rack and let cool completely. Cut into individual bars, cover and refrigerate until ready to serve. Dust the bars with confectioners' sugar before serving.