In a small bowl, add olive oil, balsamic vinegar, Dijon mustard, grated garlic, salt, pepper and whisk until smooth. Set aside.
In a large bowl, add spring mix, add half of the salad dressing and half of Parmesan cheese, then gently toss.
Spread tomatoes on top and sprinkle with remaining Parmesan cheese. You may drizzle with more salad dressing or refrigerate leftovers for another time.
Serve immediately or within an hour.
Notes
Make ahead: You can make the dressing for up to 2 weeks in advance and refrigerate. Also cut up tomatoes and grated cheese can be refrigerated in separate containers for 2 days and 2 weeks respectively.
Assemble salad right before serving. It is best to enjoy immediately as spring mix wilts quickly.