Warm the butter, sauté the fennel and apple for approx. 2 mins., season. Add the apple juice, cover and simmer for approx. 5 mins. so that they are still a little crunchy. Cook the spaghetti in boiling salted water until al dente, drain and return to the pan. Stir in the vegetables, cottage cheese, half the reserved fennel greens and the lemon juice.
Warm the butter, toast the breadcrumbs and sesame seeds, stir over a medium heat for approx. 3 mins., season with the reserved lemon zest, salt and pepper. Plate up the spaghetti, top with the crumble and garnish with the remaining fennel greens.