Remove beans from pods; discard pods. Cook beans in boiling water 1 minute; rinse with cold water. Drain; remove outer skins from beans. Discard skins. Place beans in a food processor. Add tarragon and next 4 ingredients (through garlic); process until almost smooth. Spread about 1 1/2 teaspoons bean mixture over each bread slice. Arrange cheese evenly over bread slices.