2 large yellow onions
100 g grated Parmigiano Reggiano
100 g tuna canned, drained
30 g butter
2 medium size eggs
60 g breadcrumbs
10 g triple concentrated tomato paste
1 tbsp of extra virgin olive oil
1 tbsp vegetable stock
Black pepper or chili as you like
Rock salt, to taste
Fine, to taste
Peel the onions. Blanch the outer layers in boiling salty water for 2-3 minutes, and set aside the rest. Leave to cool. Prepare the stuffing by mixing breadcrumbs, Parmigiano Reggiano, tuna, a pinch of fine salt, pepper (or chili) and eggs. Fill the onion layers.
In the meantime, chop the remaining part of the onions and cook in a frying pan with butter and oil. Once golden, add the tomato paste and a spoon of stock and let it reduce. Then sauté the stuffed layers, making sure all sides are golden.
Cover the onions in 2/3 of hot water (or the stock), and make sure to not cover the stuffing, and boil on a low heat for about 30 minutes. Make sure not to reduce the cooking liquid too much.
Tip: You can substitute the tuna with 50 g of mortadella, cut into small pieces. Then, instead of blanching the onions, you can cook them whole, without peeling off layers and cover them in aluminium foil in an oven at 200° C for about 30 minutes, or in a microwave.