Remove the stems from your strawberries and rinse them under cold, running water.
Pat the strawberries dry with a (paper) towel and divide them into two portions, one portion of around 75g, and one of around 50g.
Puree the larger portion of strawberries in a blender, or first cut them in half and mash them with a fork in a bowl. Then add the condensed milk to the strawberry puree and mix it together until smooth.
Cut the smaller portion of strawberries into small pieces. Ideally, they should be small enough to fit through a (wide) straw.
Now we're ready to start layering the Korean strawberry milk. Start by scooping the strawberry puree onto the bottom of the glass. Then place a spoon in the glass - just above the puree - and slowly pour the cold milk onto the spoon so as to not push the strawberry puree layer to the sides too much. After you've poured the milk, add the diced pieces of strawberry to the glass.
If you want you can either serve it with a straw or a long spoon to be able to stir all the layers together just before drinking it. Either way, your Korean strawberry milk is best enjoyed cold, so serve as soon as possible & enjoy!