Line a small loaf pan or 8-inch square pan with parchment, leaving overhang for easy lifting.

Arrange 9 Parle-G biscuits in a single snug layer on the parchment.

Stir espresso powder into hot water until dissolved. Let cool 1 minute so it is warm, not boiling.

With a silicone brush, lightly brush the first biscuit layer with about half the espresso. You want damp, not swimming.

Add the second layer of 9 biscuits on top. Brush the top layer more generously with the remaining espresso. Keep the bottom layer lighter so the stack stays sturdy.

Put a heavy non-stick pan on low heat. Add ghee and let it melt.

Pour in milk and stir to combine with the ghee.

Add milk powder gradually, whisking constantly to break up lumps.

Stir in sugar. Keep the heat low and stir often until the mixture thickens and starts to pull away from the pan sides after about 10 to 15 minutes.

When the mass looks like a thick, smooth paste and moves as one piece when you tilt the pan, remove from heat.

Off heat, mix in cardamom and vanilla. Work quickly while the mixture is still spreadable.

Spread the hot barfi evenly over the espresso-soaked biscuits. Press gently so the layers stick.

Dust the top with cocoa powder through a fine sieve. Add chopped nuts if using.

Cool to room temperature, then cover loosely. Let dry at room temperature at least 2 to 3 hours, or overnight for the cleanest cut.

Lift out using the parchment overhang. Slice with a sharp knife wiped with a little ghee or oil between cuts.