Heat oven to 375 degrees. Combine whipping cream, chicken broth, onion, flour, salt and pepper in 2 quart saucepan. Cook over medium heat, stirring constantly, until bubbles appear around edges and mixture is thickened (4 to 5 minutes).
Layer half of potatoes in greased 12X9-inch baking dish or 3-quart casserole. Sprinkle with ham, 1/2 cup Monterey Jack cheese and 1/2 cup Cheddar cheese. Cover with remaining potatoes.
Pour hot cream mixture over potatoes; cover. Bake for one hour and 15 minutes, or until potatoes are almost tender when pierced with a fork. Uncover; top with remaining cheeses. Continue baking for 15 minutes or until potatoes are tender and cheese is melted.