Heat the oil in a wide, medium-sized saucepan, and fry the pancetta until beginning to crisp.
Add the lamb breaking it up with a fork in the bacony pan as it browns.
Tip in the caramelized onions, Marsala, tomatoes, lentils and water and bring the pan to the boil.
Simmer the ragu for 20 minutes stirring occasionally. Sprinkle over the cheese before serving, if using.
1 tablespoon olive oil
2 cups sliced onions (about 2 medium size onions)
Heat a large saute pan over medium heat. Add the olive oil and heat. Add the onions and cook, stirring, until the onions are a deep golden brown and soft, about 25 to 30 minutes. Make sure to use a gentle heat and cook the onions slowly so they don't burn. Onions will keep in the fridge for up to 1 week.