Cook the pasta as directed. While it’s cooking, heat a sauté pan over medium heat, and add two tablespoons of the olive oil.
Add the shallots, and cook until softened, stirring frequently.
Add in the cherry tomatoes, and cook until they blister, about 5 minutes, pressing down on them with a wooden spoon to release their juices and smash them a bit.
Add the vinegar and the rest of the olive oil, and stir.
Season to taste with salt and pepper, and remove from the heat.
Drain the pasta, top with the mozzarella and the cherry tomatoes, and toss well. Garnish with the chives and serve.