Add the romaine, cherry tomatoes, red onion, olives, pepperoncini, celery, and parsley to a large bowl. Toss to combine.
In a small bowl, whisk together the champagne vinegar, Dijon mustard, and maple syrup until combined. Slowly drizzle in the olive oil while whisking continuously until the vinaigrette is emulsified. Season with salt and pepper.
Drizzle the vinaigrette over the salad and toss well to coat. Top with torn basil and shredded Parmesan. Season with additional salt and pepper to taste. Serve immediately.
Notes
Dress the salad just before serving — it wilts quickly once dressed.
The vinaigrette makes more than you need for one batch. Refrigerate the remainder in a sealed jar up to 1 week. Shake well before using.
For a vegan version, omit the Parmesan or substitute a vegan hard cheese.
Store undressed salad in the fridge for up to 2 days. Once dressed, serve immediately.