To Cook Hominy: Cover a flat baking sheet with heavy foil, arid grease or spray the foil.
In a 4-cup microwavesafe bowl, stir together grits, 1/2 cup water, and broth.
Microwave, covered, on high (100%) for 4 to 6 minutes, stirring every 2 minutes, until mixture is as thick as mashed potatoes, but not dry.
Whisk smooth and stir in 2 tablespoons cheese.
To Shape Hearts: Divide the hot mixture in half on prepared baking sheet and shape into 2 hearts, each about 1/2 inch thick, 6 inches long, and 5 1/2 inches across at the widest part, pushing up the sides to form a 1-inch raised edge.
Spray tops with cooking spray. (Hearts may be covered and refrigerated up to 2 days or frozen.
Bring to room temperature before baking.) To Bake: Place rack in upper third of oven and preheat to 500°F.
Sprinkle tops of hearts with remaining 1 tablespoon cheese.
Bake for 13 to 18 minutes, or until heated through and edges begin to turn golden. (Hearts may be baked several hours ahead and reheated at 500°F. for 2 minutes.) Remove to plates with spatula.