Finely dice the onion and sauté in hot olive oil until translucent. Squeeze in the garlic and sauté briefly. Deglaze with balsamic vinegar and let it boil down a little. Stir in sugar. Stir in the chopped tomatoes with juice and the vegetable stock, bring to the boil and simmer on a low heat for about 30 minutes.
Meanwhile cook the prawns according to the instructions on the packet. Halve the cocktail tomatoes and add to the prawns, toss briefly.
Melt the brunch tomato & ricotta in the tomato sauce. Season the sauce with salt and pepper and finally stir in the shrimp and tomatoes.