In a bowl, mix together the cornflour and ½ cup of milk and keep it aside.
Heat sugar in a heavy-bottomed pan over a medium flame.
Gently stir occasionally if needed and heat until the sugar melts. Do not stir constantly.
As the sugar starts to melt, reduce the flame to low and keep an eye on it.
Once sugar is completely melted and golden, carefully add 2 tablespoons of water and whisk to deglaze the caramel. Be careful as the caramel is very hot and may spatter.
Add remaining milk to the caramel and heat over a low flame until the hard caramel dissolves, about 8-10 minutes. Do not boil.
Then add the cornflour + milk slurry to the pan and mix well.
Add instant coffee powder and keep stirring for a couple of minutes.
Add strong brewed coffee and keep stirring over a low-medium flame until the custard thickens.
When it starts to boils, remove it from the flame and transfer it to a bowl.Place a plastic wrap directly on the surface of the custard to prevent a skin from forming on the top.
Refrigerate for 2-3 hours or until firm.Top with nuts, fruits or whipping cream before serving.
Do not use a plastic spatula while handling the caramel. Use a wooden spatula.Be careful as the caramel is very hot and may spatter.If you want your custard on the thinner side, add a little more milk.