Bring a pot of water to a boil and cook the ravioli according to the directions on the package. When done, drain the ravioli and set it aside.
While the ravioli is cooking, brown your butter. Heat a small pan over medium heat, and when the pan is hot, pop the butter in and let it melt. As it melts, add the sliced mushrooms and the sage, stirring to coat everything in butter.
The butter will start to foam as it heats up. Stir the butter, mushrooms, and sage constantly to keep the butter moving. This prevents burning.
The butter will develop a nice golden color and offer up a rich, nutty aroma. This means it's browned. At this point, the mushrooms should also be browned and tender, and the sage should be nicely crisped up.
Remove the pan from the heat and drizzle the brown butter, mushrooms, and sage over the ravioli. Gently toss the ravioli in the brown butter, and serve.