In a large bowl, add the half and half, pumpkin pie spice, paprika, nutmeg, red pepper flakes, salt/pepper, chives, garlic and whisk well. Set aside.

In another large bowl toss all the cheeses together.

In a large casserole dish (I used a 12" x 10 1/2" x 2 1/4" casserole dish), start layering ingredients, we'll have 2 layers of each. Layer half of the sweet potatoes on the the bottom of the casserole dish, followed by half of the onion slices, half of the cheese spread evenly, half of the bacon, then ladle half of the half and half mixture over the casserole. Repeat layers with remaining ingredients.

Bake for 1 hour and 15 minutes or until the sweet potatoes are fork tender. There will be some liquid in the casserole but as the casserole cools a bit, the potatoes will soak up all the liquid.

Serve warm.