On a smooth and clean surface, where we are going to work the dough, we put the flour. Shape it into a volcano (i.e., making a hole in the middle), add the egg yolks, the oil and 4 tablespoons of water. Add a pinch of salt.
With your hands, we are going to start mixing all the ingredients. Once they are well mixed we start to knead.
We will add water, very little by little, (spoonful by spoonful) if we notice the dough is too dry. Knead for about 15 minutes until you get an elastic and consistent dough that does not stick to your fingers.
Put the dough in a large bowl, where there is plenty of room, and let it rest for 20 minutes, covering it with a clean kitchen towel.
After that time, we put our dough back on the work surface and cut it into two equal parts with a very sharp knife or a dough cutter. Never stretch the dough to tear off parts of it.
Now, with a rolling pin, we have to get two very thin sheets of dough. Try to make them of the same shape, as we will put one on top of the other to make the ravioli.
When we have them ready, in one of the sheets of dough that we have prepared, we will put the filling you have chosen, teaspoon by teaspoon (do not fill too much because they must be small). And we will do it following an order. Leaving the same space between filling and filling.
Put the other sheet of dough on top of the fillings, and press with your fingers around the fillings, to join both doughs. Now, with a toothed wheel (you can use a pizza cutter) or a knife, cut the dough into small squares, in the parts where there are no fillings.
Again, press the edges of each ravioli well, so that the filling does not come out, and sprinkle a little flour over them.
We put a large pot with plenty of water, bring to boil and, when it starts to boil, we add our ravioli delicately. Cook for about 10 minutes, drain and serve with our favorite sauce.