Sausage Ragu Polenta Bowls

Name: Sausage Ragu Polenta Bowls
Ingredients: 3 cups whole milk, plus more as needed; 1 cup Semolina Flour; 4 tablespoons unsalted butter; 6 ounces mascarpone cheese; 4 ounces parmesan cheese, shredded; fresh thyme or basil to garnish; 2 tablespoons olive oil; 1 onion, finely chopped; 1 1/2 lbs spicy Italian Sausages, casings removed; 4 cloves garlic, roughly chopped; 1/2 - 1 teaspoon red pepper flakes; 2 teaspoons dried thyme; 1 24-ounce jar marinara sauce; 1/2 cup heavy cream; 1 lemon, zested; grated parmesan