Combine spices and set aside.
Butter the baking dish.
Layer the bottom of the pan with the sliced squash overlapping until the bottom is covered.
Season evenly with 1/3 of the spice mix.
Slice pears and layer them over the squash. There is no need to overlap but be sure to layer evenly.
Cover pears with another layer of squash as done before.
Do the same again with the pears.
Finish with the remaining sliced squash and seasoning.
Slowly pour 1/2 the cream over the layers so as not to disturb the layering.
Press down on layers using your hands. Pour on remaining cream and press down again.
Cover with aluminum foil and bake at 350 degrees for 1 hour.
Remove foil and continue cooking for 15 minutes or until tender when pierced with a knife.
It is best to chill the gratin overnight so the heavy cream has a chance to solidify with the squash and pears.

To serve, slice into squares and remove from the baking pan. Reheat on a cookie sheet for 5-7 minutes in a 350 degree oven.