Bring a large pot of water to a boil. Season generously with salt, add orzo, and cook according to package instructions. Drain, rinse with cold water, and drain well again.
Meanwhile, cook the broccoli. Bring 3/4 cup water to a boil in a large pot. Add a big pinch of salt and stir in the broccoli. Cover and cook for 1 minute until bright green but still slightly crunchy. Drain the broccoli in a strainer and run under cold water to stop the cooking. Drain well and set aside.
Make the pesto: Combine 2 cups of the cooked broccoli, garlic, three-quarters of the pine nuts, Parmesan, 1/4 teaspoon salt, and 2 tablespoons of the lemon juice in a food processor. Drizzle in olive oil and creme fraiche and pulse until smooth.
Toss orzo and remaining cooked broccoli florets with about two-thirds of the broccoli pesto and the lemon zest. Thin with a bit of warm water to desired consistency. Adjust seasoning by adding more salt, lemon juice, or pesto as desired. Fold in avocado. Serve topped with remaining pine nuts.