¾ cup all purpose flour
1 cup pecans, chopped
½ cup firmly-packed light brown sugar
¼ cup granulated sugar
1 teaspoon ground cinnamon
1 teaspoon ground cardamom
1 teaspoon salt
1 stick cold, unsalted butter, cut into small pieces
1 ½ cups all purpose flour
¾ cup granulated sugar
2 teaspoons baking powder
½ teaspoon ground cardamom
4 T unsalted butter, melted
3/4 cup cream
2 tsp vanilla extract
1 cup blueberries, plus more for garnish
Prepare the Pecan Streusel: Preheat oven to 350°F. Stir together chopped pecans, brown sugar, cinnamon, salt, 3/4 cup flour, 1/2 cup granulated sugar, and 1 teaspoon ground cardamom in a medium bowl. Add 1/2 cup cold butter pieces, and, using your fingers or a pastry blender, combine until a sandy texture is achieved.
Prepare the Cake: Sift together baking powder, 1 1/2 cups flour, 3/4 cup granulated sugar, and 1/2 teaspoon cardamom. Beat cream, vanilla, egg, and 4 tablespoons melted butter with an electric mixer on medium-high speed until frothy, about 1 minute. Fold in the flour mixture with a spatula until blended. Do not overmix.
Arrange the blueberries evenly over the batter, pressing them into the batter just a bit. Cover the top evenly with the Pecan Streusel, pressing lightly.
Bake in preheated oven until a toothpick inserted in the center comes out clean, about 1 hour. Cool in pan on a rack 1 hour. Remove sides of pan before serving. Serve with vanilla ice cream.