Puy Lentil and Sweet Potato Pie

Name: Puy Lentil and Sweet Potato Pie
Ingredients: 2 tbsp olive oil; 1 onion (finely diced); 2 cloves garlic (minced); 1 carrot (finely diced); 2 celery sticks (finely diced); 1 red chilli (finely chopped); 1 tsp smoked paprika; 1 tsp dried thyme; 250 g puy lentils (pre-cooked); 150 g chestnut mushrooms (finely diced); 2 tbsp tomato puree; 400 g chopped tomatoes; 500 ml vegetable stock; 1 tbsp soy sauce; Salt and pepper (to taste); 750 g sweet potatoes (peeled and chopped); 4 tbsp plant milk (if needed)