Heat the oil in a small pan and fry sage leaves until crispy. Drain on kitchen paper. Set aside.
In a bowl, mix grated Parmigiano Reggiano, cornmeal and 3-4 fried sage leaves crumbled. Heat a small skillet on a medium heat. Spread Parmigiano cornmeal mixture in a thin layer in the skillet and let it melt until crispy. Take the skillet out of the flame, let it rest for a minute or so and turn the Parmigiano cornmeal crisp briefly on the other side. Cook for a few seconds and flip it on a plate.
Cook the Tortelloni according to package directions until al dente; drain. Heat the butter in a large skillet over medium heat until the butter has melted. Add the Tortelloni to the skillet, toss and season with salt and pepper to taste.
Divide Tortelloni among plates, sprinkle with crumbled Parmigiano crisp, and garnish with fried sage and serve.