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Here is a simple vanilla custard recipe.

what you will need:
2 cups of milk
2 egg yolks 
½ cup sugar 
1 tbsp flour 
1 tsp vanilla extract

what you need to do:
Heat milk until small bubbles form around edge. Remove from heat. 
Beat egg yolks with sugar and flour until smooth.
Whisk in hot milk. Transfer to a saucepan. 
Cook over medium heat, stirring constantly, until sauce comes to a simmer. 
Cook 1 minute longer then remove from heat and stir in vanilla.