In a small bowl, mix 3 tablespoons of custard powder with 1/4 cup of cold milk. Stir well to make a smooth, lump-free paste.
In a pan, heat the remaining 3.5 cups of milk on medium flame. Let it come to a gentle boil.
Stir in the sugar and let it dissolve completely. You can adjust the amount of sugar according to your taste.
Slowly pour the custard paste into the boiling milk while stirring continuously to avoid lumps.
Keep stirring the mixture on medium-low heat for 3-4 minutes until it thickens. Once it reaches a creamy consistency, turn off the heat. Let it cool down to room temperature.
Transfer the custard to a bowl, cover it, and refrigerate for at least 1-2 hours to let it cool completely.
Once the custard is chilled, add your choice of chopped fruits and nuts. Gently mix them in.