Heat oven to 375° F. Line a cookie sheet with parchment paper.
In a Mixing bowl, cream together the butter and sugar until light and fluffy. I like to use a hand mixer for this.
Mix in the milk and the egg.
In a separate mixing bowl, combine the sour cream, pudding mix, baking soda, and salt.
Add the flour and the sour cream mixture to the butter mixture. Mix until smooth.
Add the white chocolate chips and lemon zest. Mix to combine.
Drop by rounded tablespoonfuls onto a parchment lined (or silicone mat lined) cookie sheet.
Bake at 375° F for 8-10 minutes.
Transfer the cookies to a wire rack to cool.