In a large skillet, melt the butter with garlic over medium heat. After 1 minute, add the diced vegetables, sage, and sauté on high flame for 2 minutes. Add milk, season with salt and pepper to taste and cook until vegetables are “al dente”, 5-7 minutes, and the ragout is creamy.
In the meantime, cook the Tortelloni according to package instructions and drain, reserving a little of the pasta cooking water. Add Tortelloni to the pan and toss 1 minute over medium heat adding pasta water a little at a time to loosen the ragout if necessary.
Divide Tortelloni among plates and serve. Sprinkle with grated Parmigiano Reggiano cheese if desired.