Preheat oven to 350 degrees and lightly grease a baking sheet.
In a large bowl cream together butter and sugar. Mix in cocoa powder and milk.
In a medium bowl whisk together flour, salt, baking powder, and baking soda.
Add dry ingredients to wet ingredients and mix until incorporated.
Roll dough into small balls (about 1 1/2-2 inches wide) and place on prepared baking sheet. Use your thumb to press down in the centers of the balls to make an indent.
Bake for 7-9 minutes until cookies look dry and start to crack a bit around the top. (I prefer to undercook mine a little bit so they stay very soft and chewy) Gently press down the centers again. Allow to cool.
In a microwave-safe bowl combine caramels and heavy cream. Microwave on high for 1 minute, stir, and return to microwave for 20 second increments mixing after each until smooth.
Spoon caramel into the center of each cookie. Sprinkle sea salt over the top. Allow to cool slightly before serving or store in airtight container at room temperature up to 3-4 days.