Preheat your oven to 350°F.
In a separate bowl, mix together oats, flour, brown sugar, cinnamon, and salt. Stir in the chopped nuts.
1 cup old-fashioned oats, 2/3 cup all-purpose flour, 2/3 cup packed brown sugar, 1 teaspoon ground cinnamon, 1/4 teaspoon salt
Add the cold butter pieces and use your fingers or a pastry cutter to mix until the mixture resembles coarse crumbs. Place in the fridge while you make the filling.
1/2 cup cold unsalted butter, 2/3 cup chopped pecans or walnuts
In a large mixing bowl, combine pumpkin puree, granulated sugar, brown sugar, cinnamon, ginger, nutmeg, salt, eggs, and heavy cream. Mix until smooth and well combined.
1 can 15 oz pumpkin puree, 1/4 cup granulated sugar, 1/2 cup packed brown sugar, 1 teaspoon ground cinnamon, 1/2 teaspoon ground ginger, 1/4 teaspoon ground nutmeg, 1/4 teaspoon ground cloves, 1/4 teaspoon salt, 3 large eggs, 3/4 cup heavy cream
Pour the pumpkin filling into the 10-inch cast iron skillet. Then evenly sprinkle the crisp topping over the pumpkin filling.
Bake in the preheated oven for 45minutes, or until the filling is set and the topping is golden brown and crisp.
Allow the pumpkin crisp to cool slightly before serving. It can be enjoyed warm or at room temperature, optionally with a scoop of vanilla ice cream or a dollop of whipped cream.