Wash the chana dal 2 to 3 times and soak it for about 5 to 6 hours. Drain the water, add another glass of water and little salt and a pinch of turmeric powder and cook it in a pressure cooker for 3 to 4 whistles and keep it for rest for a couple of minutes. It should be tender and firm too.
Drain out all the remaining water from chana dal. You can also cook it in an open lid. It will take about 15 to 20 minutes to cook chana dal.
Now heat oil in a pan over medium flame, add cumin seeds and curry leaves, cook it for few seconds, add ginger garlic paste, green chilly paste, turmeric powder and salt, saute for a minute.
Add chana dal and chopped onion, garam masala, cumin powder, lemon juice. mix everything and cook for a few minutes till water dries out. Now switch off the flame. Add Coriender leaves and mint leaves mix it well.
And the chana dal stuffing is ready.
Take flour in a small bowl, add water in it and make a paste. This paste will b used to sill samosas.
Take a samosa patti (samosa wrapper) and put about 2 teaspoons of chana dal filling. Fold into a samosa shape.
Heat oil and fry till the samosas are crispy and golden brown.