Line a tray or baking sheet with parchment paper. Arrange the phyllo shells on the tray so they’re ready to fill.

Cut the tomatoes and mozzarella into bite-sized pieces, then place them in a medium mixing bowl.

Slice the basil leaves into thin strips, and cut any larger pieces into smaller bits, then add them to the bowl.

Drizzle the tomato mixture with olive oil and gently toss until everything is evenly coated.

Spoon the mixture into the phyllo cups, dividing it evenly between each shell. About 2 pieces of mozzarella and 2 pieces of tomato fit well in each cup.

Finish the cups with a drizzle of balsamic vinegar right before serving.

Serve immediately for the best texture. The phyllo shells will soften and become soggy if they sit too long after being filled.