Cook pasta al dente according to package instructions. When they're done, make sure to reserve ½ cup of pasta water. Prepare all ingredients.
Add oil to a pan over medium heat. Add garlic, red chili flakes, and lemon zest. Saute for 2 minutes.
Add black pepper, nutmeg, turmeric, mustard, and lemon juice. Cook for a minute.
Add broccoli, nutritional yeast, and dried rosemary. Let broccoli soften and cook a little (~ 3-4 minutes) before adding kale and continuing to cook for 2-3 more minutes. Add milk and let it combine well with everything else. Add another 1/4 cup milk if you want it creamier.
Add reserved pasta water, take the pan off the heat, and mix in the pasta.
Top with the remaining 1 tsp of rosemary, some red chili flakes according to preference, and crushed walnuts.