Freezer Streusel

2 cups chopped walnuts
3 cups packed brown sugar
1/2 cup unbleached all purpose flour
2-3 tablespoons cinnamon
1/2 teaspoon fresh nutmeg (optional)
1/4 teaspoon salt
1 tablespoon vanilla
1 cup very cold, unsalted butter - cut into 16 chunks

Place walnuts, brown sugar, flour, cinnamon, nutmeg, salt, and vanilla in work bowl of a food processor (if processor is too small, process half a batch at a time). Pulse briefly to combine. Add butter chunks and process to make a coarse, crumbly mixture.

Freezes almost indefinitely. Makes 6-7 cups.