1) Add calamari rings to a large mixing bowl and cover with milk (use more or less to completely cover the calamari. Peel garlic cloves and gently bash with the side of a knife to open the clove and release some of the juices. Add to the bowl, season with salt and pepper, then cover and refrigerate overnight.
2) Heat approximately 7.5cm of vegetable oil to 180C in a deep-fryer or heavy-bottomed pot. Remove calamari bowl from the refrigerator, stir in the basil.
3) Set up 2 large mixing bowls: 1 with a colander sitting in it and the other with seasoned plain flour. Dump the calamari into the colander and drain the milk. shake the colander to remove excess liquid then place the drained calamari and basil into the plain flour. Toss to coat. Place back into the colander to remove excess flour. Fry (both calamari and basil leaves) in batches until crispy and golden brown, about 2 minutes. Use a slotted spoon to transfer the calamari and basil leaves to a tray lined with paper towels to drain as you cook.
4) Set a large skillet over medium heat and add 3 tablespoons of olive oil. Add chopped garlic, onion and red pepper flakes. Saute until fragrant then add tomatoes and wine.
5) Break up tomatoes with the back of your wooden spoon and simmer uncovered for 20 minutes until some of the juice has reduced. When done, give it a final seasoning with salt and pepper, then puree in a blender (or use an immersion blender) until smooth. Season with salt, pepper and sugar and serve with calamari.