Cook pasta according to package directions. Drain pasta when al dente, about 8 minutes.
In large skillet or Dutch oven over medium heat, heat butter. Add garlic and sage; saute 1-2 minutes, until garlic is lightly browned. Add cream cheese and pumpkin. Heat until cream cheese is melted and stir to combine.
Gradually stir in milk, cheddar and gruyere. Stir in Dijon mustard, salt and pepper. Heat until cheese is melted and sauce is creamy, about 3 minutes.
Fold in cooked pasta.