filling: 12 ounces cream cheese — softened
1/3 cup sugar
1 egg
1 tablespoon fresh lemon juice
1 teaspoon vanilla
streusel: 1 stick unsalted butter — softened
1 cup sugar
2/3 cups flour
1 1/2 teaspoon cinnamon
1/4 teaspoon salt
batter: 1 stick unsalted butter — softened
1 1/4 cup sugar
2 eggs
2 teaspoons vanilla
4 cups flour
1 tablespoon plus 1 teaspoon baking powder
1 teaspoon salt
1 cup milk
3 cups picked over blueberries
Preheat oven to 375 degrees and butter a 13 by 9-inch glass baking dish. Do not use a metal baking dish.
Make filling: With an electric mixer, beat together cream cheese and sugar. Add egg, lemon juice, and vanilla and beat until smooth.
Make streusel: In a small bowl blend together streusel ingredients until crumbly.
Make batter: In another bowl with an electric mixer beat together butter and sugar. Beat in eggs, 1 at a time, and vanilla and beat on high speed until light and fluffy. In another bowl whisk together flour, baking powder, and salt and in batches slowly beat into butter mixture alternately with milk. Fold in blueberries gently but thoroughly.
To assemble cake: Spread 2 1/2 cups batter in bottom of baking dish and spread filling evenly on top. Drop spoonfuls of remaining batter on filling and spread evenly (be careful not to mix layers). Sprinkle streusel evenly over batter. Bake coffeecake in middle of oven 1 hour and 5 minutes, or until golden and a tester comes out clean. Cool coffeecake completely in baking dish on a rack.