Set a steamer basket in a large saucepan. Add the broccoli and steam over high heat until bright green and just tender, about 4 minutes.
In a large skillet, combine the olive oil with the garlic and crushed red pepper and cook over moderate heat until fragrant, about 1 minute. Add the miso and butter and stir until the butter is melted. Add the broccoli, season with salt and cook for 1 minute, stirring. Transfer to a bowl and serve.