Steam small broccoli florets until very tender, then finely chop and set aside.
Cook pasta in 8 cups of boiling water with 1 tbsp salt. Reserve 1 cup of pasta water before draining.
Sauté shallot, garlic, and chili flakes in 3 tbsp olive oil over medium heat until fragrant, about 3 minutes. Stir in miso paste, then add broccoli, salt, pepper, and broth. Simmer, breaking apart the broccoli with a spatula until it forms a sauce-like consistency, adding more liquid as needed.
Stir in the lemon zest and pecorino cheese. Simmer on low until thickened, about 10 minutes. Blend for smoothness
(optional): Use an immersion blender in the pan with a handful of chopped spinach, or blend separately. The full 3 tbsp olive oil creates a rich, creamy texture.
Combine with pasta, tossing to coat, and add reserved pasta water as needed to keep it silky.
Taste & adjust seasoning with salt, pepper, and chili flakes.
Serve & customize with your favorite garnishes. Enjoy!