Combine flour, cocoa and salt. In a separate bowl cream together the butter and sugar until light and fluffy. Mix in the egg yolk, milk and vanilla. Stir in flour mixture, just until combined. Chill dough in the refrigerator for one hour.
Whisk egg whites in a bowl until frothy. Place chopped pecans in another shallow bowl. Remove dough from fridge and roll into small balls (however many cookies you want--I made 20 small ones).
Roll each dough ball in the frothy egg whites, and then roll and press in the chopped pecans. Place on a greased baking sheet.
Use the back of a small measuring spoon to make an indentation in the center of each dough ball.
Bake at 350 Degrees F for about 10-12 minutes, or just until set. Don't over-bake as cookies will harden as they cool.
As the cookies come out of the oven, gently re-press the indentations with a small spoon.
In a microwavable bowl mix the caramel bits and water. Microwave at 30-second intervals, stirring after each interval, until caramel is melted (1-2 minutes). Pour small spoonfuls of caramel into the indented cookies. *Optional: Drizzle with melted chocolate (or sprinkle with sea salt)!