In a bowl, mix the egg with the sugar and the essence. Add the zest, the olive oil, and then alternately add the sifted flour, milk, and lemon juice. • Peel the pears and cut them in half. Remove the seeds and then cut them into thin slices (without separating them). • Grease both sides of the Flip. Pour the mixture into the deepest part. Cover with the pears. • In a small bowl, mix the sugar, flour, chopped walnuts, olive oil, and cinnamon to form a crumbly mixture. • Distribute the crumble over the pears. • Close and cook over low heat for 15 minutes. • Flip the Flip and continue cooking over low heat until fully cooked.