Smoked Cheddar and Ham Potato Gratin

1 tablespoon butter
1 large shallot, chopped fine
6 oz ham, chopped
2 lbs russet potatoes, peeled, cut into 1/8 inch thick slices
3 cups smoked cheddar cheese, shredded
1 1/2 cups half and half
2 teaspoons all-purpose flour
salt and pepper to taste

1. Heat the oven to 350°F. Spray a 2 quart baking dish with cooking spray.
2. Melt the butter in a small skillet over medium heat and sauté the shallots until lightly browned, about 8 minutes. Remove from heat and set aside.
3. Arrange about 1/3 of the potatoes in the bottom of the gratin dish, overlapping them slightly. Season with salt and pepper. Sprinkle about 1/3 of the ham and shallots over the potatoes and then about 1 cup of the cheese. Repeat this process 2 more times, finishing with 1 cup of the cheese. Gently press down on the casserole. 
4. Whisk the half and half together with the flour and drizzle along the sides of the dish.
5. Bake for 1 hour and 15 minutes or until bubbly and browned and the potatoes are tender when pierced with a sharp knife. Let casserole sit for 10 minutes before serving.