1. Bring water to a boil for pasta. Cook broccoli 3 minutes following package instructions. Zest lemon (1 teaspoon), then juice (2 tablespoons). Halve tomatoes. Remove basil leaves from stems (½ cup).
2. Cut broccoli into bite-sized pieces. Cut chicken into bite-size pieces, then coat with 1 tablespoon oil, 1 teaspoon salt, and ½ teaspoon pepper (wash hands).
3. Place in bowl of food processor: lemon juice, lemon zest, basil, garlic, cheese, 2 cups broccoli, ¼ cup walnuts, and remaining 1 teaspoon salt and ½ teaspoon pepper; pulse to blend, then drizzle remaining ½ cup oil in slowly with processor running. Process until smooth and combined. Set pesto aside.
4. Cook and drain pasta following package instructions, reserving ½ cup pasta water.
5. Preheat large, nonstick sauté pan on medium-high 2–3 minutes. Place chicken in pan and cook 8 minutes, turning occasionally, or until well browned. Add tomatoes and remaining broccoli and ¼ cup walnuts to pan; cook 2–3 minutes until tomatoes start to soften and chicken is 165°F.
6. Remove pan from heat. Add pesto, pasta water, and pasta to pan; toss to coat. Divide among serving bowls and top each with 1 tablespoon ricotta, if using. Serve.

Chef's Tip: Chill leftovers and enjoy a tasty pasta salad the next day.