4 cups chicken stock
2 cups milk
1 ½ cups polenta or cornmeal
1 cup shredded fontina
½ cup grated Parmigiano-Reggiano
3 tbsp. EVOO
1 lb. sweet Italian sausage, casings removed
1 medium bulb fennel—trimmed, quartered, cored, and thinly sliced
1 large red or yellow onion, thinly sliced
4 cloves garlic, thinly sliced
½ cup white wine, or 1/2 cup chicken stock plus a splash of white wine vinegar
Heat the chicken stock and milk in a large round-bottom pan, such as a risotto pot or Dutch oven, over low until barely simmering.
Whisk in the polenta until smooth, 2 to 3 minutes; season with salt and pepper. Simmer over low heat, stirring occasionally, until thickened and creamy, 20 to 25 minutes. Stir in cheeses until melted.
In a large skillet, heat 1 tbsp. EVOO, one turn of the pan, over medium-high. Add the sausage, breaking up meat with a spoon, and cook until browned, 5 to 6 minutes. Transfer to a paper towel–lined plate. Add the remaining 2 tbsp. EVOO, two turns of the pan, then stir in the fennel and onion; season with salt and pepper. Cook until softened, about 5 minutes. Add 1/2 cup water and simmer until it evaporates. Add the garlic; stir for 2 minutes, then pour in the white wine (or the stock and vinegar). Simmer until liquid has evaporated. Return sausage to pan, stirring to incorporate.
Ladle the polenta into shallow bowls and top with fennel, onions, and sausage.