Stir in seasonings: tomato paste, mustard, tamari, cayenne and/or paprika, dried mint and dried thyme. Add lentils and frozen green peas to the pot. Mix. Cook until warmed through, then set aside.
Layer lentil filling in oiled baking dish and top with an even layer of potatoes. Bake in preheated 425-degree F/205-degree C oven 25-30 minutes until golden on top.