Preheat oven to 350°. In a medium bowl, combine pumpkin purée, spices, half-and-half, sugar, and egg, mixing well. Reserve.

. On a baking sheet, bake pumpkins and tops until they begin to soften, about 10 minutes. Remove from oven and fill with pumpkin mixture. Return to oven and bake until filling is set, 30–45 minutes. (Start checking at 15 minutes and rotate pan as needed.) Remove from oven.

In a medium bowl, combine gingersnaps, pumpkin seeds, almonds, butter, and oil, mixing well to combine. Transfer gingersnap mixture to a rimmed baking sheet and bake until dry, about 10 minutes.

To serve, place a pumpkin on six dessert plates. Sprinkle each with gingersnap streusel. Lean the pumpkin tops against the pumpkins and serve.