Preheat the oven to 180C/350F/Gas 4. Grease a large ovenproof dish with butter.
For the filling, mix together all of the filling ingredients until well combined.
Lay the blanched pasta rectangles onto a work surface. Spoon a little of the filling mixture in a line lengthways along the centre of each pasta rectangle. Roll up each pasta rectangle into a tube. Place each of the cannelloni into the prepared ovenproof dish.
For the topping, mix together the all of the topping ingredients except the pasta until smooth and well combined.
Pour the topping mixture over the cannelloni until covered. Bake in the oven for 8-10 minutes.
Preheat the grill to its highest setting. Place the cannelloni under the grill for 2-3 minutes, or until the topping is golden-brown and bubbling.
Divide the cannelloni equally among six serving plates. Serve with the lightly dressed green salad.