Heat oil in a medium nonstick skillet over medium heat. Add the shrimp, and sauté 1 minute. Add garlic, and sauté an additional minute or until shrimp are done. Remove shrimp mixture from skillet, and set aside.
Add beans, salt, and pepper to skillet; cook over medium heat 1 minute, stirring frequently. Remove from heat, and mash beans. Spread bean mixture evenly over bread slices. Divide shrimp mixture evenly among bread slices; garnish with sage leaves, if desired.