| 1 | Preheat the oven to 350°F. |
| 2 | Butter a 12-by-18-inch jelly roll pan and line the bottom with a sheet of parchment or waxed paper. |
| 3 | In a large mixer bowl, beat the butter and sugar until soft and light. |
| 4 | Add the eggs one at a time, beating well between each addition. |
| 5 | Beat in the vanilla. |
| 6 | Sift together the flour and baking powder and stir into the batter in three additions, alternating with the yolks and milk, beginning and ending with the flour. |
| 7 | Spread the batter evenly in the prepared pan. |
| 8 | Scatter the blueberries evenly over the batter, pressing them in gently. |
| 9 | for the crumbs: mix the flour, sugars, cinnamon and nutmeg in a bowl. |
| 10 | Melt the butter and stir it in evenly. |
| 11 | Rub the mixture to coarse crumbs by hand. |
| 12 | Scatter the crumbs over the berries as evenly as possible. |
| 13 | Bake the cake about 40 minutes until batter is firm and crumbs are well-colored. |
| 14 | Cool the cake in the pan on a rack. |
| 15 | Cut the cooled cake into 24 3-inch squares. |
| 16 | Remove the squares from the pan to a platter. |
| 17 | Variations: substitute 4 cups pitted sour cherries for the blueberries. |
