Step 1Melt 4 tablespoons butter in a medium saucepan over medium heat. Add the onion and garlic and cook until soft, about 4 minutes. Add the rice and stir for 30 seconds to warm and coat the grains with butter.
Step 2Add the chicken stock in three equal parts, stirring the rice constantly to release the starches. Cook until the kernels are soft enough to eat but still have a bite to them, about 27 minutes.
Step 3Trim the tough bottom of each stalk of baby broccoli, and trim the larger outside leaves while leaving the smaller ones and the broccoli sprout. Blanch in a large pot of boiling, salted water until tender, about 2 minutes. Drain and toss in olive oil, salt and pepper.
Step 4To finish the risotto, stir in the remaining butter to make a creamy consistency. Spoon onto a plate and top the risotto with the baby broccoli. Top the vegetable and risotto mound with the sliced peppered pecorino.