Bring a large pot of salted water to boil and cook pasta until al dente. With a few minutes remaining, toss in broccoli, peas, spinach and scallion and cook for 2-3 minutes.
Immediately drain pasta and veggies in colander and rinse with cold water. This prevents green veggies from cooking any longer and turning dark green (spinach will be dark green). We want to keep that bright vibrant green color!
To make the sauce: Add all sauce ingredients into large bowl and whisk away (you could also use a blender). Add water bit by bit until ricotta mixture becomes somewhat fluid; just enough to pour easily and provide a thick coating on the pasta.
Add sauce to pasta and toss until well coated. Refrigerate and add water as needed if it drys out.