CARAMEL:

80g caster sugar

2 tbsp room temperature water

2 tbsp hot water

CUSTARD:

500ml whole or full-cream milk

100g Horlicks powder

2 eggs

2 egg yolks

Pinch of salt

1. Preheat oven to 150°C and put an oven rack or tray in the middle position. Set aside four ramekins (or other oven-proof moulds that have a minimum capacity of 150ml) into a large baking dish with sides taller than the ramekins. This will be the set-up for the water bath later (see notes below for more info on what a water bath is). 
2. For the caramel: On medium heat, put sugar and 2 tbsp room temperature water in a medium saucepan. Stir with a spoon until sugar dissolves.
3. Once sugar dissolves, stop stirring. Allow mixture to bubble, and use the saucepan handle to swirl mixture occasionally so that the caramel browns evenly.
4. After 4-6 minutes, the caramel should be a dark amber. Remove from heat and immediately add the remaining 2 tbsp hot water. The mixture will sputter, so stand back at this stage until it mellows. Divide caramel between the ramekins and swirl to coat the bottoms.
5. In the same saucepan used for the caramel (no need to wash it!), add the milk and warm it over medium heat until small bubbles appear at the edges. Do not bring it to a boil. At this point, whisk in the Horlicks until fully dissolved and smooth. The residual caramel at the bottom of the pan will melt when whisked—this will add flavour to the custard and result in a more painless clean-up! Remove from heat and stir in a pinch of salt. Set aside.
6. Put a large kettle or pot of water to boil. Meanwhile, in a separate medium bowl, whisk eggs and egg yolks until smooth. Pour Horlicks and milk mixture into eggs and whisk until combined. Strain this mixture equally into your ramekins (refer to the second picture in the gallery above).
7. Pour the boiling water into the larger baking dish containing the ramekins, taking care to not get any water into the custards. The water should come up at least a third of the way up the sides of the ramekins. Bake on the oven rack or tray for 35-60 minutes (see tips below for more info on baking time).
8. To test doneness, shake the roasting dish gently. If the custard is set at the edges but wobbly at the centre, it is done. Remove ramekins from the baking dish and allow to cool at room temperature for an hour. Then, cover ramekins with plastic wrap and refrigerate until completely firm, at least 4 hours.
9. To unmold, run a knife around the edges of the custard to loosen it. Hold a plate over the top of the ramekin and quickly and assuredly invert the custard onto the plate. The caramel should cascade down the sides and bottom of the flan.