Preheat the oven to 350ºF (177ºC) and lightly grease a 9X13” (23x33cm) baking dish.
Add the pumpkin puree to a large bowl and add ¼ cup of melted butter. Mix well.
Add the heavy cream (or milk), sugar, vanilla extract, pumpkin pie spice, cinnamon, and salt. Stir well to combine.
Beat the eggs in a small bowl, then add to the pumpkin mixture and stir until smooth.
Transfer the pumpkin mixture to the prepared baking dish and smooth it into an even layer. Set aside.
Preparing the Topping
To make the topping combine ¾ cup of packed brown sugar and ½ cup of all-purpose flour in a medium bowl.
Add the butter and cut it in with two forks or a pastry cutter until the butter is in pea-sized pieces (or you can grate frozen butter and stir it into the flour and sugar mixture).
Pour in the chopped pecans and stir well.
Sprinkle the brown sugar and pecan mixture on top of the pumpkin casserole, spreading it into an even layer.
Baking
Bake in the preheated oven for 35-40 minutes, or until the edges are brown and the pecans lightly toasted.
Remove from the oven and cool for 10-15 minutes before serving (this helps the topping to crisp up).
Notes
*Sweeter: I wanted to make sure this recipe wasn't TOO sweet for most tastes, so the pumpkin layer has a very subtle sweetness. If you would like a very sweet result (similar to sweet potato casserole), scale the sugar to ¾ cup in the base layer. **Pumpkin Pie Spice Substitute: If you don't have pumpkin pie spice, you can use the following quantities of spices in place of the pumpkin pie spice called for in the recipe (it makes a little more than called for, but it's negligible).
¾ teaspoon cinnamon
½ teaspoon ground ginger
½ teaspoon ground nutmeg
¼ teaspoon allspice
¼ teaspoon cloves
Make ahead: Prepare the casserole up to 24 hours in advance and refrigerate until needed. For the best results, store the topping in a separate bag and sprinkle it on top before baking. Warm the baking dish at room temperature for 1 hour before baking to help prevent temperature shock from the hot oven. Gluten-free: This recipe is easily made by substituting the all-purpose flour for a gluten-free baking mix that measures 1 to 1 with flour (we like Bob’s Red Mill). This recipe has been tested using the gluten-free substitute with great success.Using unsalted butter: I recommend using salted butter in this recipe, but if you only have unsalted butter on hand you can add ½ teaspoon of salt to the pumpkin mixture, plus ½ teaspoon to the topping mixture.