Drowned Beef Sandwich with Chipotle Sauce (Torta Ahogada)

Ingredients (9)

• + 12 ounces chipotle cooking sauce (such a Knorr®) add to pantry
• + 1 (14 ounce) can reduced-sodium beef broth add to pantry
• + ¼ cup chopped fresh cilantro add to pantry
• + 2 tablespoons vegetable oil add to pantry
• + 1 onion, thinly sliced add to pantry
• ✓ 3 cloves garlic, minced
• ✓ 1 pound thinly sliced deli roast beef
• + 4 bolillo rolls, halved and lightly toasted add to pantry
• ✓ 4 sprigs fresh cilantro, or to taste