3 cups milk
3 tbsp corn starch
3 egg yolks
1/4-1/3 cup sugar
1/2 tsp salt
3 tbsp butter
2 tsp vanilla

Mix sugar, curb starch, salt, and most of the milk in a pot and cook on medium low until thickening.. Stirring constantly.

Mix egg yolk and remaining cold milk. Add in small amounts of hot mixture at a time to set eggs. Add to pot and cook until thickened. Add in butter and vanilla.