In a medium saucepan with a lid, bring the polenta, garlic, 4 1/2 cups water and 3/4 tsp. salt to a boil, whisking occasionally. Reduce the heat to low. Cover and cook, stirring often, until the polenta is creamy, about 18 minutes; season with salt and pepper. Meanwhile, in a large saucepan, cook the sauce, pork and peppers over medium-low, stirring, until heated through, 5 to 10 minutes. Top the polenta with the pork mixture; garnish with the shaved cheese and torn basil.