For the shortbread cookie:
In the bowl of a stand mixer, add softened butter, sugar, egg yolks and vanilla. Beat with the paddle attachment at medium-low speed, scraping the bowl often, until light and creamy. Add one third of the flour; beat at low speed until just combined, repeat with remaining flour. Cover with plastic wrap and refrigerate at least 1 hour.
Preheat oven to 375 degrees.
Roll dough into 1-inch balls. Place 2 inches apart onto parchment paper lined baking sheets. Make indentation in center of each cookie with your thumb or whatever tool you choose. Bake for 7-10 minutes or until edges JUST begin to brown.
Repeat indentation once cookies are done baking, if necessary. Cool completely on wire cooling racks.
For the caramel filling:
Melt the caramel and heavy cream in the microwave, stirring every 30 seconds or so until it is fully melted and smooth. Add pinch of salt and stir. Using a teaspoon measuring spoon, fill each indentation with the caramel.
For the chocolate drizzle:
Pour vegetable oil over chocolate chips and melt the chocolate in the microwave, stirring 30 seconds at a time until melted and smooth, and scoop into a ziploc bag. Barely snip the corner and drizzle over the cookies.