In a deep bowl put 4 cups of flour, add salt and sugar, then add an egg. Stir it very well together.
Add milk and mix it. Then add the water and continue to mix until it is blended. Now you can use your hands to knead the dough. Once the dough is elastic and soft, and doesn't stick to your hands, wrap it in a plastic wrap and put it aside for 40-50 minutes.
Meanwhile, you can prepare the meat. In a deep bowl mix together ground beef and ground turkey.
For onion, it is better if you grate it instead of dicing it. The onion will produce juice that you also will add to the ground meat. It will make the meat softer and will bring the flavor.
Finally, just add the salt and pepper to the meat and mix it very well.
When the dough is ready, knead it again until its soft and elastic, adding some more flour. Cut a piece of the dough (about an apple size) and roll it evenly until it is thin (about 1/2 centimeter).
Cut the circles from the dough using a glass or a special circles cutter. Put about 1 teaspoon of meat in each circle and make the shape of the ravioli.
When the raviolis are ready, you can cook some of them and put the rest in the freezer. It will stay there good at least for a week. In order to cook, boil the water in a deep pot, and cook raviolis in rolling boiling water for 10 minutes. They are done! I like to fry them after cooking, adding a teaspoon of butter, to have a little bit of crust. I believe it tastes better that way. And you can experiment with different toppings on the side of your choice: ketchup, sour cream, mayo, mustard, or anything you like.
When you cook the raviolis from the freezer, you don't need to defrost them. Just put them into the boiling water and cook for 10 minutes as the fresh ones. They will come out delicious!