Preheat oven at 175C.
Spray an oven dish with baking spray & let it set.
In a pan, heat up the oil & melt the butter.
Add the chicken mince to the pan & season it with the chicken seasoning. Break apart into small bits. Cook for 7 minutes over high heat, stirring occasionally.
Add the onions & garlic to the pan & season everything with some salt & pepper. Cook for 8 minutes over medium to high heat, stirring occasionally.
Add the mushrooms & spinach to the pan. Close the pan, lower heat & cook for 12 minutes. After the 12 minutes, remove any liquid from the mixture.
After, add the besciamella. Bring to a boil & then turn off the heat.
In a separate bowl, mix the ricotta, salt, pepper, parsley & garlic powder well together.
Start assembling the lasagna by layering first a layer of the lasagna sheets. Then spread the chicken mixture over & layer another layer of lasagna sheets on top. Spread half of the mixture of the ricotta & again layer a layer of lasagna sheets on top of the ricotta. Repeat with the chicken mixture, lasagna sheets & finish with the remaining ricotta on top.
Cover the dish with aluminium foil & cook in the oven for 60 minutes.
Remove the foil & spread the mozzarella slices on top. Continue cooking in the oven for 20 minutes.
Let it cool a bit when done cooking & then serve.