Preheat the oven to 180 degrees Celsius/ 350 Fahrenheit.
Grate the pumpkin coarsely. Cut the chicken breasts into very small pieces.
Make lasagna sauce: Heat a large pan over moderate heat and add the curry paste. Stir well for 1 minute, then pour in the coconut milk. Fill the empty can with water and add that to the pan as well. Bring everything to a boil, add the lemon juice and the soy sauce, and let simmer for about 3 minutes.
Add the chicken and pumpkin to the pan, bring to a boil, reduce heat, and cook, covered, until everything is soft, about 10 minutes but check. The sauce should still be quite runny; if it is not, add a bit more water.
Assemble lasagna: Spread ¼ of the sauce in a rectangular pan of about 30x20 cm/ 12x9 inches. Cover with lasagne sheets. Add another ¼ of the sauce, lasagne sheets, another ¼ sauce, lasagne sheets, and ¼ of the sauce again. You should have 4 layers of sauce and 3 layers of lasagne sheets.
Mix the cheese and the breadcrumbs and sprinkle them over the last sauce layer.
Bake in the hot oven for 30 minutes or until the pasta is cooked through and the cheese is golden brown. Turn off the oven and let sit inside for another 10 minutes.