In a large pot of boiling, salted water, cook pasta according to package instructions. Drain well.
To make the avocado sauce, combine avocados, basil, garlic and lemon juice in the bowl of a food processor. Season, to taste, with salt and pepper. Still mixing, add olive oil in a slow stream until emulsified. Set aside.
Put a bit coconut oil in a pot. Cook sliced mangold, plantains, onion and celery for about 10 minutes.
In a large bowl, toss pasta, avocado sauce, and vegetables. Serve and enjoy this creamy heaven.
Just don’t heat an avocado for more than a few minutes, since cooking turns the fruit bitter.