Makes about 64 small ravioli, or slightly less if you make them larger. You can serve 4-5 ravioli as an appetizer, which is how I typically serve them in restaurants.
Grind the toasted mushrooms to a powder. Pour the boiling water over the mushroom powder and salt to make a paste, then cool the mushroom mixture.
Whisk the egg yolks into the mushroom mixture, then add to the flour in a stand mixer with the paddle attachment and mix until the mixture starts to come together—it may look crumbly, so mash it a bit with your hands to come together.
Switch to the dough hook and knead to a smooth ball, about 1 minute more. Remove the dough and knead a bit by hand, it may feel firm at first, but as it rests it will soften.
Filling
For the filling, pour the water over the mushroom powder and salt, then mix with the ricotta, parmesan, nutmeg if using and egg. Pack the filling into a pastry bag, or use two spoons for making the ravioli.
A pastry bag is much faster. If your filling seems rough, or has chunks of parmesan in it, consider buzzing in a food processor to make it smooth.
Assembly
Cut the dough into 4 pieces, keeping the excess wrapped in a towel or cling film as you work. Roll the dough out to the thinnest setting of the pasta roller, then cut each length in half to make 2 manageable sheets. Square the edges off a bit to make them rectangular, or if they don’t fit on your cutting board.
Brush the dough very lightly with water, then pipe 8 teaspoons or so of the filling in the middle of the dough sheet, fold the dough over, and remove as much air as you can. Press down all around the ravioli, then cut with a fluted cutter.
Gently transfer the ravioli to a baking sheet, not allowing them to touch, and dusted with cornmeal or semolina (all purpose flour will make them stick and tear). As you fill up baking sheets, transfer them to the freezer, or refrigerate if cooking within an hour or two.
Cooking
To cook, bring a pot of salted water to a boil. Drop the ravioli into the water and cook until they float. If you want to cook them from frozen (what I usually do) you’ll need to cook them for a bit longer. When in doubt, taste them.
If they’re still tough after floating coming out of the freezer, keep cooking a bit longer. Toss the cooked ravioli with simple garnishes: some wilted greens, melted butter, olive oil parmesan cheese, sauteed mushrooms or a light butter sauce.
Notes
Toasting Toast dried mushrooms at 350 for a few minutes in a skillet--just until they're aromatic. When in doubt, toast less rather than more. Because the mushrooms are not rehydrated for this recipe, they also must be very clean. Freezing for storageRavioli can be frozen and cooked straight from the freezer, just increase the cooking time a bit.