Adapted from: Land O'Lakes
1/2 Cup Butter, melted
1/2 Cup Water
1 Cup Butter, softened
3 1/2 cups Powdered Sugar
1/3 Caramel Sauce
1 t Vanilla
Cookies - Combine cake mix, butter, water and eggs; beat at medium speed until smooth.
Cover and place in fridge for 15 minutes to rest.
Drop heaping teaspoons full of batter onto tray. Gently press into desired shape with fingers (Cookies will not change much from initial shape after being baked)
Sprinkle with sea salt and bake for 5-7 minutes then transfer to cooling rack.
Filling - Beat butter at medium speed until creamy. Reduce speed to low; gradually add powdered sugar. Beat until well mixed. Add caramel sauce, salt and vanilla. Beat until well mixed.
Pipe filling onto flat side of 1 cookie; place second cookie, flat-side down over filling. Repeat with remaining cookies and filling.