Cook the Italian sausage in a skillet over medium high heat until completely browned.
Add the minced garlic to the sausage, and sauté for another 30 seconds.
Mix in the baby spinach with the meat, and cook until just wilted. Remove the skillet from the heat, and allow the meat mixture to cool slightly.
While the meat is cooling, combine the ingredients for the dough in a mixing bowl. Blend and knead the ingredients until a crumbly dough is formed. If the mixture will not stick together and is too dry, you can add water as needed until it forms a more cohesive dough.
Let the dough sit for a few minutes.
Add the ricotta cheese and parmesan cheese to the meat mixture, and stir to combine well.
Roll the dough out between two pieces of parchment paper. You want to get the dough as thin as you can without it ripping when you lift it up.
Cut the dough into even squares.
Place a spoonful of the filling mixture in the center of the dough squares, and place another square of dough over top of it. Press the dough down gently all around the filling to create the shape of the ravioli. You can crimp the edges of the raviolis with the tines of a fork to make sure they are sealed well. If your dough is splitting open over the filling, it may not be rolled thin enough.
Boil some water on the stove, and add the raviolis to it. Cook for 2-3 minutes until they begin to soften.
Place the 4 tablespoons of butter into a skillet on the stove and sauté the raviolis in it for a minute or two.
Pour the remaining browned butter into a small bowl to spoon over the raviolis before serving. Add grated parmesan as garnish if you desire.