Cook the onions with olive oil in medium heat, fry until they become clear. Add the garlic and chicken bouillon and stir, add the pulled chicken breast and mix together. Season with salt and pepper to taste. Reserve.
Make a bechamel sauce heating 1 cup of milk, add butter and flour. Whisk to combine, gradually add the remaining 1/2 cup of milk until the sauce has a light texture.
Build the lasagna in a baking dish with layers of bechamel sauce, lasagna pasta sheets, the cooked chicken, ricotta cheese and mozzarella. A standard baking dish should hold 3 to 4 layers.
Bake in oven at 350°F for 20 mins or until outer layer acquires a golden brown color.