Place cooked butternut squash in a medium sized mixing bowl and using a fork, mash it thoroughly until smooth.
Season your mashed butternut squash with salt, black pepper and cayenne pepper. Mix well.
Now, add one egg yolk, half a cup of mascarpone cheese, and 1/3 cup of grated Parmesan cheese to the mashed squash, and mix thoroughly until all the ingredients are smoothly combined.
Spread a wonton wrapper over a clean working surface. Dip the tip of your finger in water and use it to moisten the outer edges of the wonton wrapper. You can also brush the edges of the wonton wrapper with egg white.
Place about 1 teaspoon of squash filling in the centre of the wonton wrapper, and fold it in half to give it a half moon shape. Press the edges to seal, and transfer the stuffed ravioli to a plate lined with paper towels or tissue papers.
Repeat the process with the remaining wonton wrappers and squash mixture.
Fill a saucepan with lightly salted water and bring it to a boil over medium high heat. Drop the stuffed ravioli into the boiling water, 3 to 4 at a time, and cook for 3 to 5 minutes, or until they are tender and float to the top.
Meanwhile, melt two tablespoons of unsalted butter in a deep skillet over low heat and fry the unpeeled garlic clove in it for one minute.
Drain the ravioli from the boiling water and transfer them to the skillet. Turn the heat to medium high and cook the ravioli until they are infused with the garlic flavour - this should take about a couple of minutes.
Top the cooked ravioli with grated Parmesan cheese, sprinkle finely chopped sage and freshly ground black pepper over the top, and serve hot.