Preheat oven to 210°C (190°C fan forced). Heat half the oil in a large frying pan over moderately high heat. Add mince; cook, stirring with a wooden spoon to break up lumps, for 5 minutes or until cooked. Transfer to a large bowl. Wipe pan clean.
Heat remaining oil in same pan over moderately high heat. Add leek and zucchini; cook and stir for 5 minutes or until softened. Add spinach; stir until just wilted. Transfer to bowl; cool. Add half the ricotta, half the tasty cheese, the egg white and half the pesto to mince.
Place lasagne sheets on a flat work surface. For each cannelloni, place 1/3 cup of mince mixture along a short edge, then roll up to form a tube. Place tubes side by side, seam-side down, in a lightly greased 30 x 23 x 4cm (base measurement) ovenproof dish.
Combine remaining pesto and 1/4 cup water in a bowl. Spoon over cannelloni, then sprinkle with remaining ricotta and tasty cheese. Bake for 30 minutes or until golden and cooked. Serve with salad.
Try this with beef or pork and veal mince instead.