Place the potatoes in a pot and cover with water. Boil over medium heat for 20 minutes or until fork tender but not mushy. Drain and allow to cool, then peel and cut into bite sized cubes. Set aside for mixing.

In a dry pan over medium heat, toast the sesame seeds until they begin to pop and release a nutty aroma, about 2 to 3 minutes. Stir constantly to prevent burning. Remove from heat and grind coarsely using a mortar and pestle.

Heat the mustard oil in a small pan until it begins to shimmer. Add the fenugreek seeds and let them sizzle until dark brown but not burnt. Remove from heat and immediately add the turmeric powder. Swirl to combine and set aside to cool slightly.

In a large mixing bowl, combine the cubed potatoes, chopped green chillies, red chilli powder, ground sesame seeds, and salt. Mix gently to coat the potatoes evenly without breaking them.

Pour the warm, spiced mustard oil over the seasoned potatoes. Mix gently to distribute the oil throughout the dish, allowing it to coat each piece and enhance the earthy flavour.

Add lemon juice to the mixture, starting with one tablespoon and tasting as you go. The acidity should lift the dish and balance the richness of the oil and spices.

If using ginger paste, add it now and mix gently. This adds a subtle background heat and depth without overpowering the other flavours.

Fold in the chopped coriander just before serving. Let the dish sit at room temperature for at least 15 minutes to allow the flavours to meld. This resting time improves both taste and texture.

Serve the Aloo ko Achar at room temperature as a side dish with rice, beaten yoghurt (dahi), or flatbreads. For presentation, scatter extra sesame seeds and a few coriander leaves over the top. It can also be served chilled for a sharper flavour contrast.