Heat a medium nonstick skillet coated with cooking spray over medium-high heat.
Add garlic; saut 1 minute.
Add spinach; cook 1 minute or until spinach wilts.
Remove from heat.
Combine water and broth in a large saucepan over medium-high heat; bring to a boil. Gradually add polenta, stirring constantly with a whisk. Reduce heat to medium; cook 20 minutes, stirring frequently.
Remove from heat; stir in spinach mixture, salt, and pepper.
Spoon polenta mixture evenly into a 9-inch springform pan coated with cooking spray. Press plastic wrap onto surface of polenta; chill 2 hours or until firm.
Preheat oven to 40
Remove polenta from pan; place on a baking sheet coated with cooking spray.
Sprinkle the cheese evenly over polenta.
Bake at 400 for 15 minutes or until cheese melts and begins to brown.