In food processor, combine beans, garlic, water, tomato paste and Worcestershire sauce. Cover; pulse using on and off switches 5 or 6 times or until beans are coarsely chopped. Spread 1/4 of bean mixture on each toast slice. Top with onion and avocado. Serve each with lime slice to squeeze over top, if desired.

Serving Suggestion: These open face sandwiches are easy to eat, but if you prefer, you can make them using individual thin sandwich loaves so there is a top and bottom piece of bread. You can also construct them as wraps using flour tortillas or sandwich wraps. These also make great handheld appetizers when spread on small toasts.