Whisk ¼ cup balsamic vinegar, 2 Tbsp. Dijon mustard, 2 tsp. honey, ½ tsp. onion powder, ½ cup extra-virgin olive oil, 1 tsp. salt, and 1 tsp. pepper in a medium bowl until emulsified. Add finely chopped shallots, rinsed cannellini beans, and finely grated Parmesan; toss to combine. Chill for at least 1 hour.

Arrange leaves of 2 large romaine hearts on a platter. Drizzle with oil, season with salt and pepper. Spoon bean mixture over the leaves and scatter with fried onions and shaved Parmesan.