Preheat oven to 350 degrees and line 3 baking sheets with parchment paper.
In a large bowl, cream butter and sugars together until smooth and light yellow in color.
Add in the sea salt and baking soda and stir to combine.
Stir in egg, vanilla extract, and milk and mix well.
Add flour, half at a time, mixing until just combined.
Fold in chocolate chips and Reese's Pieces.
Using a 3 TBS cookie scoop, scoop dough onto lined baking sheets two inches apart.
Bake for 12 minutes, rotating halfway though.
Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Store in an airtight container for up to 1 week or freeze.
Notes
*I only get 6 cookies per half-sheet size baking pan.**Both the cookies and the cookie dough may be frozen. Bring dough up to room temperature prior to baking.