Preheat the oven to 400F; spray an 8-9 inch pie dish with nonstick spray, and set aside.
In a large bowl, whisk together the pumpkin, milk, heavy cream, and eggs until well-incorporated.
Add in the sugars, pumpkin spice, and eggs, and whisk vigorously. Pour into the pie dish and set aside for now.
Now, let's make the brown butter. In a small nonstick pot, heat the butter over medium-high heat until completely melted.
Turn the heat down to medium-low and start whisking as the butter bubbles and fizzes. As soon as it turns medium to dark golden and starts to smell nutty, take it off the heat! You don’t want it to burn!
Whisk in the brown sugar and pumpkin spice, then add in the flour and oats. Mixture should be clumpy!
Sprinkle the streusel atop of the pumpkin mixture, and set in the oven.
Bake uncovered for 35 minutes at 400F, then cover and raise the heat to 450F for the last 10-15 minutes. Cobbler should be firm around the edges and just a tiny bit jiggly in the center {it will firm as it cools}. Enjoy warm or at room temperature with whipped cream!