Heat oil in pan over a medium heat. Add the onion, garlic, celery and carrots then reduce the heat to low and cook for approx. 10 mins (until softened.)
Add the curry powder and cook for a further minute
Add the lentils & stock, bring to the boil, then reduce the heat to low and allow to simmer until cooked, soft and stock absorbed (approx. 20 mins)
Meanwhile, heat a little oil in a pan and fry the sweet potato cubes, on a low heat, for approx. 10min. (add a little water if needed)
Pre heat oven to 180C/350F/Gas4
Once lentils are cooked, allow to cool slightly and then add the potato, egg and peas. Stir until combined.
Place the mixture in a greased, ovenproof dish (mine was 10" x 7.5")
Bake in the oven for 30-40 mins or until set and golden (mine took 35 mins) but timings will vary with ovens.
Slice into squares. I cut into 20 pieces.