Potatoes au gratin with onions, mushrooms, and bacon

Ingredients

• 3 libras russet potatoes, peeled and sliced thinly
• 1 libra sliced cremini mushrooms
• 1 large onion, sliced
• 1 clove garlic, chopped
• 6 slices bacon, cooked and crumbled
• 3-4 cups heavy cream
• kosher salt and freshly cracked black pepper, to taste
• pinch nutmeg
• 2 cups shredded aged cheddar
• dried thyme