Brush each aubergine slice with olive oil and place on a very hot griddle pan. Grill for 2-3 minutes per side. Remove from the pan and set aside. Continue until all the aubergine slices have been grilled.
For the tomato sauce, sweat the onion and garlic until soft and translucent in a splash of olive oil in a large oven-proof pan. Add the tomatoes and seasonings and allow to simmer for 10 minutes.
To make the ricotta filling, combine all the ingredients and mix well.
To make the involtini, place a dollop of the ricotta filling onto a slice of aubergine and roll up. Place in the tomato sauce and continue until all the aubergine slices have been used.
Top with the mozzarella cheese then place in the oven and allow to bake for 10-15 minutes until golden and bubbling.