Crispy Broccoli With Cheddar Polenta

Name: Crispy Broccoli With Cheddar Polenta
Ingredients: 1/2 cup extra-virgin olive oil; 8 garlic cloves, thinly sliced; 2 cups whole milk; 2 teaspoons Diamond Crystal kosher salt, plus more to taste; 3/4 cup coarse polenta (not instant); 1 1/2 pounds broccoli, cut into florets; 1/2 teaspoon red pepper flakes, plus more to taste; 6 ounces sharp cheddar, coarsely grated (about 1½ cups); 4 ounces low-moisture mozzarella, coarsely grated (about 1 cup); 2 tablespoons unsalted butter; 1 large lemon