Place the cut potatoes in a large saucepan and cover them with cold, generously salted water. Bring the water to a boil, reduce it to a steady simmer, and cook for 15–20 minutes, until a fork slides easily into the potato pieces.

While the potatoes cook, prepare the bacon until crisp. Drain and crumble it, reserving 1 tablespoon of bacon fat if you want a richer finish.

Drain the potatoes thoroughly and return them to the warm saucepan. Let them stand over low heat for 1–2 minutes so excess moisture can evaporate.

Warm the milk or cream with the butter and minced garlic in a small saucepan. Heat just until the butter melts and the mixture is warm; do not let it boil.

Mash the potatoes with a potato masher or ricer. Mix in the pumpkin puree, warm milk mixture, Parmesan, salt, pepper, and optional nutmeg.

Fold most of the crumbled bacon into the potatoes, reserving some for the top. Taste and adjust the seasoning before transferring the potatoes to a serving bowl.

Finish with the reserved bacon, extra Parmesan, and chopped parsley or sage. Add a small drizzle of reserved bacon fat for a rich deluxe finish, if desired.