Bring the 4 quarts of water and 1 tablespoon (15 ml / 0.5 fl oz) of kosher salt to a rolling boil in a large pot.
Add the penne and cook according to package directions, adding the fresh green beans for the last 5 minutes of cooking time.
Before draining, use a ladle to reserve 1 cup (240 ml) of the starchy pasta water.
Drain the pasta and beans, return them to the hot pot, and cover to keep warm.
While the pasta cooks, heat the olive oil in a large skillet over medium-high heat.
Add the sweet pepper strips and cook for 5 minutes, stirring occasionally until they begin to soften.
Add the minced garlic and cook for 30 seconds more until fragrant.
To the skillet, add the sun-dried tomatoes, fresh herbs, and the drained pasta and green bean mixture.
Cook, stirring frequently, until everything is heated through.
Stir in the balsamic vinegar and about 1/2 cup (480 ml) of the reserved pasta water to start.
Continue adding pasta water until the sauce reaches your desired consistency.
Season generously to taste with additional kosher salt and black pepper.
To serve, divide the pasta among four bowls and top with the vegan mozzarella cubes.
Garnish with extra fresh basil leaves, if desired.
Don't skip reserving the pasta water! The starches in the water help the balsamic vinegar cling to the pasta, creating a silky sauce instead of a watery one.
