In a large bowl add flour, cocoa, and 3 eggs. Slowly mix them well. Next, gradually stream in water while the mixer is running and a ball of dough forms.
Knead the dough until it is tacky (but not sticky). Then wrap the dough in a plastic wrap and chill for an hour minimum in the refrigerator.
In a small bowl add mascarpone, 1 egg, 2 tablespoons of sugar, and vanilla. Mix well, then place in the fridge until ready to use.
When the dough is ready, divide into 4 pieces. Using a pasta machine (or rolling pin), one at a time, roll out each piece from the widest to thinnest setting. Keep remaining pieces covered and in the refrigerator until ready to use.
To assemble: Lightly dust clean work surface with flour. Place one pasta sheet on the work surface. Place a teaspoon of filling every 3 inches down the pasta sheet. Fold the dough over, and press around filling to seal.
Using a 2" ravioli cutter (or pastry wheel) cut out ravioli. Set ravioli on a baking sheet lined with a silicone mat or parchment paper. Continue with remaining dough. Refrigerate until ready to cook.
To cook the ravioli, bring water and 2 tablespoons of sugar to a boil in a large pot. Add ravioli (do not crowd pot, do this in batches). When pasta floats to the top leave it for an additional 2 minutes or until al dente.
Remove ravioli with a slotted spoon. Drizzle with sauce of choice.