Drowned Beef Sandwich with Chipotle Sauce (Torta Ahogada)

Combine chipotle cooking sauce beef broth and 1/4 cup chopped cilantro in a saucepan; bring to a boil. Reduce heat to medium-low and simmer stirring occasionally for 10 minutes.

Heat oil in a skillet over medium-high heat; saute onion until softened about 5 minutes. Stir garlic into onion and cook for 1 minute. Add roast beef and 1/4 cup chipotle sauce mixture and cook stirring constantly until heated through about 2 minutes.

Ladle remaining chipotle sauce mixture into 4 bowls for dipping. Spoon roast beef mixture onto the bottom half of each bun top with a cilantro sprig and place the top on each bun. Dip sandwiches into sauce.