Heat a large sauté pan over medium-high heat for several minutes. Once hot, add the grape tomatoes and sauté, stirring constantly, until browned and burst. Set aside.
Bring the vegetable broth to a simmer in a medium saucepan, but do not let it boil. Keep warm.
Heat 1 tablespoon of the oil in a large saucepan over medium-high heat. Add the rice and cook for 2 minutes, stirring constantly. Add the wine to the pan, and stir constantly until the liquid is nearly absorbed, about a minute. Stir in 1 cup of broth; cook for 5 minutes or until the liquid is nearly absorbed, stirring constantly. Reduce heat to medium. Add the remaining broth, 1/2 cup at a time, stirring constantly until each portion of broth is absorbed before adding the next (about 25 minutes total).
Meanwhile, place vinegar in a small, heavy saucepan; bring to a boil over medium heat. Cook until slightly syrupy and reduced to 1 tablespoon (about 4 minutes).
Stir the half-and-half, salt, and pepper into the risotto; cook for 2 minutes. Remove from heat; stir in burst tomatoes and basil. Place about 1 cup of risotto into each of 6 shallow serving bowls. Add a spoonful of mascarpone and a drizzle of balsamic syrup to each. Serve hot.
Notes
To store leftover risotto, place it in an airtight container and refrigerate it for up to 3 days. While you can freeze it for up to a month, the texture might change a bit.To reheat, gently warm the risotto on the stove over low heat, adding a splash of broth or water to restore its creamy consistency. Avoid reheating in the microwave to prevent drying out.