| | Topping: |
| 1 1/2 cups | All purpose flour |
| 1/2 cup | Sugar |
| 1 tsp | Grated lemon peel |
| 1 tsp | Ground cinnamon |
| 10 tbsp | Chilled, unsalted butter, cut into pieces |
| 1 cup | Chopped walnuts |
| | Filling: |
| 8 cups | Fresh blueberries (about 2 1/2 lbs) |
| 3/4 cup | Sugar |
| 2 tbsp | Fresh lemon juice |
| 1 1/2 tbsp | Cornstarch |
| 1 1/2 tsp | Ground cinnamon |
For Topping: Whisk first 4 ingredients in bowl to blend. Add butter and rub in with fingertips, pressing until moist clumps form. Mix in nuts. (Topping can be made 1 day ahead. Cover and chill.)
For Filling: Preheat oven to 375. Place blueberries in 13x9x2-inch glass baking dish or 3 quart round baking dish with 2-inch-high sides. Add sugar, lemon juice, cornstarch and cinnamon to berries; toss gently to blend. Spread berry mixture evenly in dish; sprinkle topping over. Bake until topping is brown and filling is bubbling thickly, about 50 minutes. Cool.