Cook the cannelloni according to the instructions on the pack
In a frying pan, put the butter, oil, onion and saute a little then add the chicken breast after its wilted
Stir until the color changes and add the tomato cubes and the tomato paste and flavor it with salt and pepper
In a saucepan, add the butter and flour and turn until the flour changes color. Then add the milk and stir with the hand blender quickly until it is not lumped and saute it with salt and pepper.
Add the Parmesan cheese to the chicken and stuff the cannelloni
In the Pyrex dish, put a little of the bechamel sauce in the bottom and add the stuffed cannelloni at a slightly spaced distance
Put the rest of the bashamel sauce on the top and spread the mozzarella cheese and put in a hot oven at 200 degrees for 15 minutes.