Egg-Bacon Toasts with Onions and Spinach

Preheat oven to 450 degrees. In a large ovenproof skillet, cook bacon over medium until crisp and browned on both sides, 7 minutes; drain on paper towels. Pour off all but 1 tablespoon fat from skillet. Season onions with salt and pepper and cook, cut side down, until golden, 5 to 7 minutes. Flip, add broth, and transfer skillet to oven. Bake until onions are tender when pierced with a knife, 15 minutes.

Meanwhile, crumble bacon into small pieces. Drizzle each toast with 1/2 teaspoon oil and spread with mustard. Top each toast with 1 egg, season with salt and pepper, and sprinkle with bacon. Divide toasts and onions among 4 plates. Place skillet over medium-high and add 1 teaspoon oil and garlic; cook until fragrant, 30 seconds. Gradually add spinach and cook, tossing, until wilted. Season spinach to taste with salt and pepper and serve with toasts and onions.