Preheat oven to 350°F (175°C) and grease a 9-inch baking dish.
Whisk pumpkin puree, eggs, brown sugar, heavy cream, cinnamon, ginger, nutmeg, and salt until smooth.
Pour the pumpkin filling into the prepared baking dish and spread evenly.
Combine flour, oats, brown sugar, cinnamon, and salt in a separate bowl.
Stir in melted butter until clumps form.
Scatter the streusel evenly over the pumpkin filling.
Bake for 40–45 minutes, until the streusel is deep golden brown and the center has only a slight wobble.
Cool for at least 45 minutes before serving.