Preheat and Prepare: Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking dish. For easy cleanup, place the baking dish on a larger, rimmed baking sheet.
Make the Pumpkin Filling: In a large bowl, whisk together the pumpkin puree, lightly beaten eggs, heavy cream, ¾ cup brown sugar, pumpkin pie spice, vanilla extract, and salt until completely smooth. Pour the mixture evenly into the prepared baking dish.
Make the Streusel Topping: In a separate medium bowl, combine the flour, crushed ginger snaps, rolled oats, ½ cup brown sugar, chopped pecans (if using), and cinnamon. If using, stir in the chocolate chips Add the cubes of cold butter.
Cut in the Butter: Using your fingertips, a pastry blender, or two knives, cut the butter into the dry ingredients until the mixture resembles coarse, pea-sized crumbles.
Assemble and Bake: Sprinkle the streusel topping evenly over the pumpkin filling. Bake for 50-60 minutes. The crisp is done when the topping is deep golden brown and the filling is mostly set. The very center should have a slight jiggle to it (it will finish setting as it cools).
Cool and Serve: Let the crisp cool on a wire rack for at least 20-30 minutes before serving. This allows the filling to set properly. Serve warm.