Grease a round baking tray with ghee, taking care to cover the bottom and sides of the tray well.
Place a pan with sugar and lime juice on a low flame. Bring to a boil till syrupy (or till a 2-thread consistency). See the note below (at the far bottom of the article) for a tip on ascertaining a 2-thread consistency. Don’t fret if you can’t get it, as it needs to be light and syrupy unlike that required of a 1-thread syrup.
Remove from the stove and keep aside.
Separately take the custard powder (or corn flour) in a non-stick vessel, add all the water and stir until there are no lumps.
Turn on the heat, on a low-medium flame. Pour the diluted custard/cornflour slurry in a pan and place the pan on the stove. Stir continuously until the mixture turns thick. Add food colour at this stage and stir in the sugar syrup – in small batches. Don’t add the syrup all at one go as it won’t achieve the jelly like consistency required of a Bombay ka halwa. If you can’t figure out how jellified it must get, use a timer to cook for around 15 minutes on medium-high flame. Don’t stop stirring constantly, an exercise that pays off till its glutinous end.
Add cardamom powder, and 3-4 tsps of ghee – one tsp at a time – cooking on medium heat and stirring continuously. When it achieves the required gooeyness, remove from the stove and pour the mixture into the pre-greased tray.
Let cool, for say a half hour (or less) using your discretion. Run a thin knife around the inside edges, place a flat dish over the container and overturn it adroitly. When you hear the sound of a dollop of a drop, you know you’ve got it right.