Mix flour, egg, 2 tbsp olive oil, salt, and water into a dough. Knead until smooth - 5 minutes per YummCook, or 6 to 7 minutes by hand and about 4 minutes in a mixer per Afghan Cooks. Cover with a cloth and rest at room temperature for 30 minutes. (Skip this step if using gow gee wrappers.)
Heat oil in a heavy-based pan over medium heat. Cook the onion until soft, add the garlic, then the minced meat. Add cumin, ground coriander, dried mint, salt, pepper, and turmeric. Cook 10 minutes or until browned, breaking up the mince. Stir in fresh coriander and let the filling cool. (For the traditional raw method, season the meat and skip this cooking - see the shaping step.)
Roll the rested dough thin and cut into circles or squares at a thickness of 2 mm.
Place a small spoonful of filling in each wrapper. Dab the corners with water and draw two opposite corners together at the center to seal, then join the remaining two. Press all seams firmly.
Grease the steamer rack. Arrange the mantu without overcrowding. For browned filling, steam 10 to 15 minutes (thin wrappers) up to 15 to 20 minutes (2 mm dough), until soft and translucent - or 3 to 4 minutes for very thin pre-made wrappers. For raw filling, steam 30 to 35 minutes until the meat is cooked through.
Make the yogurt sauce: mix 1 cup yogurt, crushed garlic, ½ tbsp dried mint, and salt. Keep cold.
Make the tomato sauce: soften the onion in oil, stir in tomato paste, tomatoes, and 60 ml (¼ cup) water. Simmer 10 minutes; add lentils if using. Serve warm.
Spread yogurt on the plate, top with mantu, spoon over the warm tomato sauce, add more yogurt, and scatter with coriander.