Preheat your oven to 350°F and grease a 13 x 9-inch baking dish with butter. Set aside.
In a large bowl, combine the pumpkin puree, heavy cream, sugars, flour, pumpkin pie spice, salt, eggs, and vanilla using an electric mixer. Beat for about 1-2 minutes, just until well-mixed. Pour this mixture into the prepared baking dish and spread it evenly.
For the topping, mix together the oats, brown sugar, and flour in a separate bowl. Cut in the cold butter using a pastry blender, two knives, or your mixer on low speed, until the mixture has a crumbly, pea-sized texture. Sprinkle the topping evenly over the pumpkin filling.
Bake for 40-50 minutes or until the center is mostly set, with just a slight jiggle when you gently shake the pan.
Let the pie sit for 20-30 minutes before serving. Serve warm, topped with a scoop of vanilla ice cream or a dollop of whipped cream for an extra treat.