Line two sheet trays with silicone mats or parchment and set up a stand mixer with the paddle attachment.
Whisk together All-Purpose Flour (2 1/4 cup), Unsweetened Cocoa Powder (1 tablespoon), and Salt (1 pinch) in a medium mixing bowl. Set aside.
Cream together Butter (1 cup), Granulated Sugar (1/3 cup), and Dark Brown Sugar (1/3 cup) in the stand mixer until fluffy.
Pour in Vanilla Extract (1/2 teaspoon), followed by the yolks of the Egg (2).
Finally, turn the speed to low and slowly add in the dry ingredients until you have a lovely dough.
Use a 1.5 inch cookie scoop to scoop perfect mounds of the dough and round each scoop into a ball. Lay them out on the two sheet trays as you form them. Using that measurement, there should be 30 cookies total with 15 per sheet. They don’t really expand so just leaving a little room is fine.
Use your thumb to make a big indentation in the center of each ball of dough, then put the trays in the refrigerator to chill for an hour.
Preheat oven to 350 degrees F (175 degrees C).
Bake the cookies for about 14-15 minutes, until they just start to crisp around the edges and bake through. Use your thumb to gently press down any rising in the indentations when they come out, then let them cool for a minute. Then transfer them to a cooling rack and start on the filling.
Combine Caramel Candy (26) and Heavy Cream (3 1/2 tablespoon) in a medium microwave-safe bowl and heat them in the Panasonic Microwave Oven on high for about a minute. Stir them together, then microwave it again for about another 30 seconds. When you stir them together after this, it should be really smooth and easy to work with.
Use a heaping teaspoon to fill the indentation in each cookie, maybe more if your thumb is bigger than mine. Accounting for that, you may have more caramel filling than you need.
Once you fill all the cookies, sprinkle them generously with Sea Salt (to taste) on top. Let them set completely in the refrigerator, then store them in airtight containers to enjoy or give away! Cooking results may vary depending on microwave oven used.