Place oven rack on upper middle position and preheat oven to 425 degrees. 

Heat large oven safe, or 12” cast iron skillet, over medium high heat and add the olive oil. Once it starts to shimmer, add in the broccoli, peppers, onions, garlic, salt and pepper, and red pepper flakes. Cook until the vegetables have started to soften and brown slightly, about 10 minutes. Remove from the heat and place them into a bowl. Set them aside. 

Into the same skillet, add in the milk and chicken broth, ½ tsp salt and ¼ teaspoon of ground pepper. Bring the mixture to a boil. Whisking constantly, slowly pour in the instant polenta. Reduce the heat and continue to cook until the polenta has thickened, about 2-3 minutes. Turn off the heat. Stir in the cheese and butter until both are melted. Pour the sauteed vegetables over the top of the polenta, and nestle the sausages on top of it all. Bake until the sausages are browned and reach 160 with an instant read thermometer, about 25-30 minutes. 

Remove from the oven and allow to rest for 10 minutes before serving. Sprinkle with fresh minced parsley before serving.