03Cook bacon in large skillet until crisp. Transfer to paper towels to drain. Heat remaining 2 tablespoons olive oil in large pot over medium heat. Add shallot and sauté 2 minutes. Add spinach and stir until just wilted. Fill 12-inch-diameter skillet with water to within 1/2 inch of top. Add vinegar and 1/2 teaspoon salt. Bring to boil over medium-high heat. Break 1 egg into small custard cup, being careful to keep yolk intact. Gently slide egg into boiling water; repeat with remaining eggs. Simmer until eggs are softly cooked, about 3 minutes.
04Meanwhile, fill each bread hollow with spinach; top with bacon, breaking bacon slices in half to fit. Place in oven until heated through, about 5 minutes.
05Place 1 bread on each of 4 plates. Using slotted spoon, place 1 poached egg atop each. Sprinkle with salt and pepper.