Tortellini with Creamy Butternut Squash

3 cups Cubed Butternut squash
1 Shallot, chopped
Few Leaves of Fresh Sage
1/4 cup of Heavy Cream
1/2 cup of Freshly Grated Parmigiano Reggiano
8.8 oz Bag of Three Cheese Tortellini
5 cups of Vegetable Stock
2 Tbsp of Olive Oil
Salt and Pepper, to taste