Take the frozen berries out of the freezer and place them on the kitchen counter to thaw.
Grease the pumpkin bowl with vegetable oil and place it on the baking sheet.
Bake at 400F for about 30 minutes to 1 hour, depending on the size of the pumpkin. To check if the pumpkin is cooked, just pierce the flesh with a fork. If it goes in easily, the pumpkin is done.
Once the pumpkin is cooked through, add the berries into the pumpkin bowl and bake for another 10 minutes, until the berries are heated through. Meanwhile, prepare the ice cream.
Place the frozen banana in a food processor and blend until smooth. (While blending, banana will look crumbly at first, but don't worry, keep blending and the magic will happen soon).
Top the hot pumpkin-berry bowl with walnuts and banana ice cream before serving.
