1 stick of unsalted butter (or half butter, half lard)
12 red or white onions, sliced in thin half circles
1/8 cup all-purpose flour
1/2 cup dry white win
1/4 cup milk
6 cups of beef or vegetable stock
2 large eggs
Salt and freshly grounded black pepper
6 slices Tuscan or country bread
¼ cup extra-virgin olive oil
2 to 3oz of bone marrow roughly chopped (optional)
Freshly grated Parmigiano-Reggiano to taste
In a heavy bottom pot large enough to hold all of the ingredients, melt the butter and lard (if used) at low heat. Add the onion and cook slowly stirring often until they are caramelized or deep brown color, should be more or less half an hour. Sift the flour to avoid lumps and add it to the pot, continue cooking for 15 minutes or until is blended completely by stirring every 5 minutes or so.
Add the bone marrow (optional), wine, milk, and stock slowly and stirring constantly. Bring up the heat a little bit for a rolling simmer (moving a little), cover and cook for another half hour.
Mix the eggs and Parmigianino together with a spoon, not a wisk, to avoid incorporating air into it and add it slowly but an at even pace, season with salt and pepper to taste, turn off the heat, cover again and let it rest for about 7 minutes.
While is resting, grill or toast the bread, drizzle with olive oil and place one piece of toast at the bottom of each bowl and ladle the soup on top of it and serve.