Melt butter in a large skillet over medium-high heat. Add almonds. Stir occasionally until almonds begin to turn brown and the milk solids in the butter turn brown, 5 to 6 minutes.
Add the garlic and cover with the haricot vert, salt, and pepper. Reduce heat to medium, cover pan with a lid or foil, and steam 3 minutes. Uncover and cook, stirring, until beans are just tender, about 5 minutes.
Stir in mint and serve. Top with extra mint if desired.