Remove tops from pumpkins and hollow out with a spoon.
Melt butter in skillet over medium heat, add onions, lower heat to low, cook onions until soft and caramelized.
In a pot, add potatoes, caramelized onions, gruyere, thyme, garlic, salt, and heavy cream and mix thoroughly. Cook over med heat until cheese has melted.
Add heated mixture to pumpkins evenly and roast pumpkins at 350 for 15-20 minutes.
Top with Butternut squash puree and serve.