Cooking butter until lightly browned is a simple way to add rich nutty flavor to an otherwise straightforward dish. In this recipe, I added fresh oregano and red pepper flakes to the butter as it browns, to infuse the fresh herb and a bit of heat into the butter.
Bring a large pot of salted water to a boil. Add the green beans and cook until crisp-tender, about 2 minutes; drain and transfer to a bowl of ice water. Let cool, then drain.
Melt the butter in a large pot over medium heat. Add the oregano sprig and red pepper flakes. Cook, swirling the pot, until the butter is browned, 5 to 7 minutes. Add the green beans and 3/4 teaspoon kosher salt. Continue to cook, tossing, until the green beans are glazed, 2 to 3 minutes. Discard the oregano sprig, then add the oregano leaves to the pot and toss. Top with flaky salt and more red pepper flakes.