Whipped Sweet Potatoes with Hazelnut Topping

1/3 cup packed brown sugar
1 teaspoon grated orange rind
1 tablespoon fresh orange juice
1 teaspoon salt
1 1/2 teaspoons ground cinnamon
1 teaspoon ground nutmeg
1/4 teaspoon ground allspice
3 (29-ounce) cans sweet potatoes, drained and halved
3 large egg whites
Cooking spray
1/2 cup chopped hazelnuts, toasted
1/2 cup packed brown sugar
1/4 cup all-purpose flour (about 1 ounce)
1/4 teaspoon ground cinnamon
3 tablespoons chilled butter, cut into small pieces

Preheat oven to 400?.

Combine first 8 ingredients in a large bowl; mash well. Beat egg whites with a mixer at high speed until stiff peaks form. Gently fold beaten egg whites into sweet potato mixture. Spoon mixture into a shallow 3-quart baking dish coated with cooking spray.

Combine hazelnuts and next 3 ingredients (through 1/4 teaspoon ground cinnamon) in a bowl. Cut in butter with a fork until mixture is crumbly. Sprinkle over sweet potato mixture. Bake at 400? for 25 minutes or until topping is lightly browned.
from Cooking Light.