Add the milk powder, corn flour, food coloring and vanilla to a food processor or blender, then blend for about 10 seconds.
Transfer to an airtight container and store in the pantry.
To Turn It Into Custard:
Add 1/2 cup of custard powder to a small saucepan with the sugar and milk. Whisk to combine, then heat over low heat stirring constantly until thick and beginning to bubble. Add more milk if you want a thinner consistency.