Whisk half and half, vanilla extract, and sweetened condensed milk in a large bowl.
Add cocoa to the mixture using a mesh strainer or a sifter.
Add in the coffee and whisk until well combined.
Pour in the whiskey and allow the mixture to stand for 10 minutes. During this time the instant coffee granules will absorb liquid making it easy to mix everything together.
Taste the mixture. Adjust the amounts of cocoa, vanilla, coffee granules, or whiskey, if necessary.
Use a funnel to pour the Irish cream into a jar with an airtight lid.
Refrigerate the Irish cream for at least four hours before serving.
