In ungreased pan on medium high heat, toast peppercorns for 30 to 60 seconds, or until fragrant. Constantly move pan to prevent burning. Remove from heat and let cool. With mortar and pestle, grind coarsely.

In small bowl, whisk yogurt, oil, Parmesan, lemon juice, ground peppercorns, minced garlic, and salt until emulsified. Set aside.

Halve romaine heads vertically. On hot grill, place heads cut side down and cook until charred, about 1 to 2 minutes.

Arrange grilled lettuce heads on serving plate, add beans directly on top of grilled romaine, and drizzle with dressing. Top with additional flake salt and toasted bread crumbs, if desired.