The night before, rinse the lentils and pick through any odd looking ones. Rinse until the water runs clear then place in a large bowl and cover with clean water. Leave overnight to soak
Drain the lentils and set aside. In a small skillet, add a drizzle of oil and cook the onion and garlic until softening. Add the spices and cook, stirring 2 minutes. Add lentils and cook a few more minutes.
Add the lentils and onions mixture to the food processor. Add the breadcrumbs and egg and pulse 10-20 seconds or until the mixture has come together but still has some texture. Add milk to adjust consistency if needed.
With wet hands scoop out about 2 tablespoons of the mixture and form into a patty. Repeat to form 6-8 patties
Preheat a pan with about 2 cm of oil in the bottom, when the oil is hot add the patties in a single layer. Cook 4-5 minutes each side, until nice and brown and crispy.
Serve with yoghurt sauce
For yoghurt sauce: In a small bowl, add the greek yoghurt then stir through the lemon juice, garlic cloves and a pinch of salt and pepper. Mix well, then serve with a drizzle of chilli oil and some toasted cumin seeds.