Cut the pork and chicken breast into 1/2-inch cubes, keeping them ready to cook.
Melt the butter in a skillet over medium heat. Add the pork with one or two pinches of salt and grindings of pepper. Cook 6 to 7 minutes, turning to brown evenly. Remove with a slotted spoon and let cool.
Add the chicken to the same skillet with a pinch of salt and pepper. Brown on all sides about 2 minutes. Remove with a slotted spoon and let cool with the pork.
Once cool enough to handle, chop the pork and chicken together until grainy and slightly coarse. A food processor is fine, but do not puree it.
Put the chopped meat in a bowl and add the mortadella, ricotta, egg yolk, grated Parmigiano-Reggiano, and a tiny grating of nutmeg (about 1/8 tsp). Mix until evenly combined. Taste and adjust salt.
Make yellow pasta dough by the machine method or hand-rolled method. Cut and shape tortellini, stuffing with the filling. When boiling the pasta, add 1 tbsp olive oil to the water.
