Thinly slice potatoes and add to boiling water. After a couple of minutes add green beans to the water. Cook your pasta. Aim to have potatoes, pasta, and beans all ready at the same time (arithmetic may be involved).
Meanwhile, heat pesto gently in a pan with about half a teaspoon of flaked dried chillis. When the other ingredients are ready, drain, add to the pesto, and, er, stir and eat...