In the same pot, melt the butter in the olive oil. Add the garlic and cook over moderately high heat, stirring, until lightly browned, about 2 minutes. Add the cabbage and potato along with the rosemary and thyme and season with salt and pepper. Cook until slightly dry, about 2 minutes. Add the pasta with its cooking water and cook, stirring and breaking up the potato, until the sauce is creamy and thick, about 2 minutes. Remove from the heat and stir in the Fontina and the 1/4 cup of Parmigiano. Transfer the pasta to bowls and serve, passing extra grated cheese at the table.