It's a gratin! No quantities or details because you can do whatever you want, I'm not the boss of you.
Filling
Fry some onions and carrots. Spice it up with herbs like thyme and rosemarine. Deglaze with red wine and veg stock if you wanna. Add some lentils
Topping
Potatoes, sweet potatoes and olive oil. Slice thin and toss together
Bechamel Sauce
Fry some margarin and flour. Add oat milk and then oat cream. Season with white pepper, nutritional yeast and a bit of miso!
Oven
Put it all in an oven pan and cook at like 200c. I won't tell you how long!
No nice picture because I was too busy eating, but here are some leftovers!