Gather all the ingredients. Dry grind the whole spices fenugreek seeds (methre), mustard seeds and jeera. Chop the green chillies.
Take mustard oil in kadai (heavy bottomed pan) and let it burn for few min. Once it cools off a bit (color changed from dark yellow to light yellow), add heeng, haldi, saunf, red chilli powder.Add garlic and cook for a min.
Add green chillies. Add salt and black salt (kala namak) and mix well. You may cover with lid for less than a min.
Add the ground masala and Amchur (Mango Powder). If you dont have Amchur, you may use 1-2 tsp lemon juice. Mix really well and switch off the flame.
The garlic green chilli pickle is ready. Keep the jar in sun for few days. One may start eating it in 2 days itself.