Cook the potatoes in salted boiling water till just done. Drain and keep aside.
To prepare the chutney, grind together coriander, mint, garlic, ginger and green chillies to a fine paste.
Heat oil in a pan and add the cumin seeds, followed by the green chutney; mix to combine.
Sauté on low heat for 2 minutes, stirring often and then add turmeric, coriander powder, garam masala and amchur powder.
Mix well and continue to cook on low heat for a minute, stirring so as not to burn the spices.
Add the cooked potatoes and toss well through the masala.
Taste and season with salt if necessary. Squeeze the lemon juice and toss well before removing from heat.
Garnish with roasted sesame seeds.