1. Bring 5 litres of water to a boil in a large pan.
2. Place butter and sage in a 10 to 12-inch pan over medium-high heat and cook until butter turns golden brown and spatters a bit.
3. Add the pumpkin puree and remove from heat; it will make some noise here and be a little messy.
4. Swirl the pan to mix the butter and pumpkin mixture together and set aside.
5. Drop the three cheese tortellini into the boiling water and cook according to packet instructions; drain in a colander and immediately toss the cooked tortellini into the pan with the pumpkin mixture, place over medium heat and toss until pasta is coated with sauce.
6. Mix in half of the grated Parmigiano and toss 10 seconds, then pour into a heated bowl and serve immediately.