Step 1: Preheat oven to 375 F.
Step 2: Bake 4 large sweet potatoes (about 2 pounds) for 45 minutes until soft. Remove potatoes from oven and let cool slightly.
Step 3: Peel sweet potatoes and place into the bowl of an electric mixer. Add 1/4 cup butter, 1/2 cup half-and-half, 1/2 cup maple syrup, 1 teaspoon ground cumin, 1/2 teaspoon ground cinnamon and 1/2 teaspoon ground nutmeg. Season with salt and pepper to taste. Beat with electric mixer on medium speed to smash potatoes or use whisk attachment on high speed to whip until smooth.
Step 4: Spread into an 8-by-8-inch baking dish sprayed with no-stick potatoes cooking spray.
Step 5: Sprinkle 1/2 cup prepared granola over top. Dot granola with remaining 2 tablespoons butter cut into pieces and drizzle with remaining 2 tablespoons maple syrup.
Step 6: Reduce oven heat to 350 F. Bake 30 minutes until top is golden and casserole is heated through.