Cream together butter and sugar. Add egg and vanilla extract and beat until well blended.
Whisk together flour, Diamond Crystal(R) Fine Sea Salt, baking powder and baking soda in a separate bowl. Add dry ingredients to wet ingredients and mix until just combined. Form in 2 balls. Cover bowl with plastic wrap. Refrigerate for 1 hour.
Preheat oven to 350 degrees F. Line a baking sheet with parchment paper.
Roll out each ball to 1/4 inch thickness on a sheet of waxed paper sprinkled with confectioner's sugar. Cut out circles or little shapes using a small 1 1/2-inch cookie cutter. Place on prepared baking sheet. (Note: If dough becomes too soft when rolling out, place back in the refrigerator.)
Bake 5 to 7 minutes. Allow cookies to cool on the baking sheet for 5 minutes. Remove cookies and place on wire rack to cool.
Salted Caramel Filling: Use a microwave safe glass measuring cup. Remove wrappers from caramels. Add caramels, Diamond Crystal(R) Fine Sea Salt, and heavy whipping cream to measuring cup. Microwave using 20-second intervals, for approximately 1 minute. Stir after each interval.
Chocolate Ganache: Use a 1 cup measuring cup. Add 1/4 cup of heavy cream. Microwave until the cream starts to bubble. (Approximately 25-30 seconds.) Remove the heavy cream from the microwave. Add chocolate chips. Let the mixture rest for 2 minutes. Then stir with a spoon until smooth.
To make sandwich cookies, add 1/2 teaspoon of caramel and 1/2 teaspoon of chocolate ganache to the bottom side of half the cookies. Top with another cookie to make a sandwich cookie.