Heat 1 tablespoon oil in an ovenproof skillet over medium-high. Add onion; sauté 4 minutes. Add garlic; cook 30 seconds. Add greens in batches, stirring to wilt. Add stock, pepper, and salt. Reduce heat, and simmer 12 minutes. Stir in cheeses and farro.
Preheat broiler with oven rack in top position.
Combine remaining 1 1/2 teaspoons oil and panko in a bowl; sprinkle over pan. Broil 4 minutes or until golden.