Line two large rimmed baking sheets with parchment paper and set aside.

To a large mixing bowl add the unsalted butter and granulated sugar. Beat on medium-high speed, using a handheld or stand mixer, for 1-2 minutes or until light and fluffy.

Add the egg yolks and vanilla extract to the bowl and beat again for another 1-2 minutes or until the egg yolks are fully incorporated.

Add the all-purpose flour and salt to the bowl and mix on low speed for 2-3 minutes or until the dough comes together to form a rough ball. The cookie dough should be thick and not crumbly.

Using a 1 inch (approximately 1 tablespoon) small cookie scoop, scoop out a level amount of cookie dough. Place the dough into the palm of your hand and gently roll to form a smooth ball. Place the rolled cookie dough ball onto one of the prepared baking sheets and repeat until all the dough balls have been formed. The dough balls should be placed about 1-1 ½ inches apart on the baking sheet.

Using your thumb, or a small (½ teaspoon) rounded measuring spoon, press an indent into the center of each rolled cookie dough ball. You can dip your thumb, or the back of the measuring spoon, into a small amount of flour to keep the dough from sticking when being pressed. Be sure to smooth together any cracked edges that may form when pressing the dent into the center of the cookie dough balls.

Place the baking sheet of formed thumbprint cookies into the freezer to chill the cookies for 30 minutes. This will help to ensure that the cookies hold their shape, and do not spread too much, when baked.

Preheat the oven to 350°F.

Remove the baking sheet from the freezer. On the second prepared baking sheet, place 12 chilled thumbprint cookies approximately 2 inches apart. Place the first baking sheet back into the freezer while each batch of cookies bakes.

Bake the thumbprint cookies for 13-14 minutes or just until lightly golden around the bottom edges of the cookies.

When the cookies come out of the oven, you may need to gently press down the indents in the center of each cook as they may puff a little when baking. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a large cooling rack to cool completely.

Repeat steps 9-11 until all the thumbprint cookies have baked and cooled.

In a medium bowl, add the unwrapped soft chewy caramel candies and the heavy cream. Microwave on high for 30 seconds, stir and microwave again in 30 second increments, being sure to stir the caramels in between each heating, until the caramels are fully melted and stirred to a smooth consistency.

Using a small scoop, or teaspoon measure spoon, spoon a little less than 1 teaspoon of the warm caramel sauce into the center of each thumbprint cookie being careful not to overfill the indentation of the cookie.

In a small bowl, melt the milk chocolate wafers according to package directions (in the microwave for 30-40 second increments stirring between heating times) and stir until smooth.

Transfer the melted milk chocolate to a small piping bag with the end snipped off, or use a small spoon, and drizzle the milk chocolate across the tops of all the cookies in a decorative pattern. If adding the optional garnish of flaky sea salt, you will need to sprinkle a small amount onto the cookies while the caramel and milk chocolate are still soft to ensure the flaky sea salt sticks to the cookies.

Allow the twix thumbprint cookies to sit for 10 minutes, to allow the chocolate drizzle to harden, before plating and serving.