Start a large pot of water boiling for the pasta and salt it well. Once boiling, add the pasta and cook according to package directions, or until al dente.

Add the olive oil and garlic to a skillet and heat on medium-low. As soon as the oil is heated, add the cherry tomatoes and basil. Raise the temperature slightly, then add the red pepper flakes and salt (and sugar if using).

Cook, stirring, until the skin on the cherry tomatoes starts to crack open, being careful not to brown the garlic. If it starts to color, add a tablespoon or two of water.

When the tomatoes start cracking, use the back of a large spoon to smash about half of the cherry tomatoes. Add the butter (if using) and stir to combine.

Once the pasta is ready, spoon it out with a slotted spoon, allowing excess water to drain off, and add it to the skillet with the tomatoes. Stir to combine and add a half ladle of pasta water. Cook the pasta with the sauce for about 2 minutes, then season with freshly ground pepper.

Remove the skillet from heat and stir in the cubed fresh mozzarella, allowing the residual heat to soften the cheese. Serve immediately with freshly grated Parmesan and thinly sliced fresh basil.