Transfer the espresso beans to a sealed plastic bag, and lightly crush them.
Add the crushed espresso beans and the heavy whipping cream to a small saucepan. Set the mixture over medium heat and bring it to a simmer.
Once the mixture is simmering, turn the heat off and allow the mixture to sit for at least 5 minutes, up to 20.
Break up the milk chocolate baking bar into small chunks and add it to a large mixing bowl.
Once the cream has sat for 5 minutes, put it back on medium heat. Once the mixture starts to simmer again, pour it through a fine-mesh sieve over the chocolate.
Cover the bowl with a lid or plate. Let the mixture sit for 1 minute, then whisk the ingredients together until you have a smooth ganache.
Transfer the ganache to the freezer, and stir every 5-10 minutes until it has significantly thickened up.
Once the ganache has cooled and thickened, use a hand mixer to whip up the mixture until it is fluffy and has lightened in color.
Transfer the whipped ganache to a piping bag fitted with your tip of choice, and pipe it on to half of the cookies.
Sandwich the cookies, serve, and enjoy!