Place the ciabatta in a food processor or blender and whizz to form chunky breadcrumbs. Heat the oil in a small frying pan, add the garlic and stir around the pan, then add the breadcrumbs. Cook for 5–7 minutes until golden and crisp all over, then remove from the pan and set aside.
To make the anchovy sauce, mash the anchovies on a board, using the back of a large knife, to form a paste. Place in a bowl and mix in the mascarpone, then stir in the lemon juice, egg and Parmesan.
Cook the pasta in a large saucepan of salted boiling water according to the pack instructions until al dente. Drain, reserving a little of the cooking water, and return to the pan. Stir in the anchovy sauce and mix together well, adding a little cooking water to loosen if needed. Season, then toss through the rocket leaves.
Spoon into serving bowls and serve scattered with the breadcrumbs.