Crack egg into a medium bowl and mix in milk stirring well with a fork
Add oats, onion, cheese, and salt & pepper and mix well then add ground beef and combine
Spray cupcake/muffin tin with nonstick spray and press meat down into each cup. I had exactly enough for 12.
Mix ketchup, mustard, and brown sugar and put a spoonful on each meat cake.
Bake for about 25 minutes or until internal temp. reaches 160 degrees.
While meat cakes are baking make the potatoes according to package directions. I used Idahoan roasted garlic flavor and add the butter and cream cheese. Let them cool slightly and then put most of the potatoes into a frosting bag with your favorite decorating tip. If you don't have these, you can put into a large Ziploc bag and cut off the corner of the bag or just put a scoop on with a spoon.