Dewberry roll

2 cups all-purpose flour;

2 teaspoons baking powder;

1 teaspoon fine sea salt;

2 tablespoons sugar;

2 tablespoons butter, cut into small cubes and chilled;

2 tablespoons vegetable shortening or lard;

1 large egg;

1⁄2 cup milk;

2 tablespoons butter, at room temperature;

2 cups fresh dewberries or other blackberries;

3⁄4 cup sugar;

1 large egg beaten with 1 tablespoon cold water, for an egg wash;

Sweet Corn;

Custard Ice Cream;

Vanilla ice cream, or whipped cream, for serving.

Whisk together the flour, baking powder, salt, and sugar in a large bowl. Add the butter cubes and drop the shortening in bits over the flour mixture and toss to coat. Use your fingertips to work them in until the pieces are the size of garden peas. In a small bowl, whisk together the egg and milk, pour over the flour mixture, and stir with a fork or your fingertips until the dough comes together.
Pour the dough onto a lightly floured sheet of parchment and gently knead until the dough is smooth, about 5 turns. Roll or pat the dough into a rectangle that is 1⁄2-inch thick, turned so one of the long sides is at the bottom. Spread the soft butter evenly over the dough. Scatter the berries over the butter, leaving the bottom 2 inches bare. Sprinkle the sugar over the berries. Starting at the top, roll up the dough toward you, making sure it is tight enough to hold the berries in place. It should look like a jelly roll. Pinch the seam and the ends closed. Transfer the roll (still on the parchment) to a rimmed baking sheet. Brush the top and sides with the egg wash.
Bake until the pastry is browned and any escaped juices are bubbling, about 35 minutes. Cool on a wire rack for 10 minutes before slicing and serving with ice cream or whipped cream.