Bring a large pot of salted water to a boil. Add the green beans and cook until just tender, 3 to 5 minutes.
Meanwhile, melt the butter in a skillet or small saucepan over medium heat. Stir with a wooden spoon as it starts to foam. Remove the butter from heat as soon as it begins to turn golden brown and smell nutty, about 1 minute. Add the garlic, pine nuts, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Swirl the skillet over heat for 30 seconds more to coat the nuts. Spoon the mixture over the green beans and serve.
Make-Ahead Note: This dish can be partially prepared up to 2 days in advance. Blanch the green beans by boiling until tender. Plunge them into an ice bath to stop the cooking. Drain and refrigerate, covered, until ready to add the butter mixture. Cook the green beans until heated through.