Make the Boston Cream Custard following the steps in the recipe HERE. Then scrape it into a small bowl and set it aside to cool while you make the rest of your filling.
In a large mixing bowl, beat the heavy cream until stiff peaks almost start to form. Add the sweetener and vanilla extract and beat again just until it's the texture of regular whipped cream.
In another bowl, beat the cream cheese until light and fluffy.
To bring everything together, add the custard and cream cheese to the whipped cream and beat well until smooth and thick.
Bringing It All Together
Break your cookie into pieces and add it to the filling mixture, stir gently to combine (I like to reserve a little for topping later).
Use a long and thin cookie cutter or what I use, the end of a turkey baster (lol) to cut out holes out of the center of the cupcakes. You want to press ALMOST to the bottom but you still want a thin bit of cupcake left. Repeat this for all of the cupcakes.
Use a piping bag with an open end or a plastic ziplock bag with the end cut off to pipe the filling into the cupcakes, then top them in a circular motion as you would regular cupcakes.
Sprinkle any additional keto oreo cookie you reserved and you're done! Chill for ~30min then you can serve them at room temperature if you wish. Enjoy your Keto Cookies and Cream Cupcakes!