Heat the oven to 375 degrees.
In mixer bowl with the paddle attachment, add combine the brown sugar, peanut butter, shortening, milk & vanilla. Beat until well combined.
Add the egg - beat until just blended.
Add in flour, baking soda & salt. Beat until just blended.
Fold in the mini chocolate chips.
Take small 1 teaspoon size sections & roll into balls & place on ungreased cookie sheet.
Press flat with your fingers. You should be able to fit close to 25-30 mini cookies on your cookie sheet & they should be no larger than 1 inch in diameter. Preferably a bit smaller as they will spread a little when baking.
Bake 8 minutes and remove. Allow the cookies to cool 1-2 minutes on the baking sheet before transferring to wire rack to finish cooling.
Store in an airtight container for up to 4 days.