Cook pasta according to directions for al dente, minus one minute in salted water (pasta will finish cooking in the skillet). Drain, reserving ¾ cup of the starchy pasta water right before draining.
Add green veggies to food processor (or other blender), squeeze juice of lemon over them. Add also the pine nuts, a drizzle of olive oil, and pine nuts. Pulse until you have a very finely minced texture.
Add the avocado, blend until incorporated. Set aside.
Mince garlic and shallot/onion. Dice chicken. In a skillet, heat olive oil/butter on medium high heat; add shallot/onion, garlic and diced chicken.
Saute until caramelized and browned. Remove just the chicken pieces (leaving the garlic and shallot in pan) and set aside on a plate; this prevents them from overcooking and becoming though.
Pour sherry into the pan to deglaze, still on medium high heat.
Simmer on medium high heat until reduced by half, it should look thickened, darker and all the browned bits removed from the bottom. The bottom of the pan is "clean" and smooth.
Now comes the magic. Reduce heat to low. Add the cooked pasta to the skillet, along with the processed greens/pine nut/lemon/cheese mixture and chicken pieces.
Add half of the starchy cooking water, more Parmesan , whole pine nuts if desired, and juice of the other half of the lemon and toss to combine. Salt and pepper to taste. Remove from heat.
Serve immediately, and garnish with extra Parmesan and pine nuts. Salt and pepper to taste, if necessary.
Adjust the amount of pulsing or blending to fit your needs. More pulsing/blending results in a finer texture that resembles a pesto sauce. If you prefer larger pieces of green, pulse/blend less.