Preheat oven to 350˚F. Line two sheet pans with parchment paper. Set aside.

In the bowl of an electric mixer, beat butter and sugar till soft and fluffy, this will take 2-3 minutes. Add salt and vanilla bean paste (or vanilla extract) and mix for a few seconds to combine.

Add flour and mix for 1-2 minutes, (stopping a few times to scrape the sides of the bowl) until large crumbs form. Pour mixture out on to a work surface and knead several times, if needed, until a smooth ball forms.

Scoop up small balls of dough, about 2 tablespoons each. Roll each ball between the palms of your hands till you form smooth, round balls. If dough is difficult to roll into balls, refrigerate for about 10 minutes, then proceed. Place dough balls on prepared cookie sheets, spacing 2 inches apart and pressing on each one just a bit with the palm of your hand.

Flatten each disc of dough with a flat-bottomed glass to a disk about ½ inch thick.

Make an indention, about ½ inch in diameter in the center of each dough disk. Use your thumb or any round-ended utensil to make the indentions, such as the end of a wooden spoon or ice cream scoop. If cookie crack along the edge when making indentions, just push the dough back together.

Place sheet pans with prepared cookies in the refrigerator for 15-20 minutes before baking. This will keep them from spreading out too much.

Bake for 15-18 minutes or until beginning to turn golden at bottom edges. When cookies come out of the oven, reinforce the indentations a bit, if needed.

Remove to a wire rack to cool slightly.

When caramel is beginning to thicken, fill the center of each cookie with a generous rounded teaspoon of the caramel mixture.

Sprinkle lightly with flaky sea salt. Allow to cool and "set" for at least an hour before serving.

For the caramel:

Combine the butter, brown sugar, cane sugar, corn syrup and heavy cream. Bring to a boil stirring till dissolved.

Reduce heat to a steady simmer and cook, stirring occasionally until mixture reaches 220˚F* on a candy thermometer. Remove from heat and add vanilla. Stir well until smooth and bubbles disappear. Allow caramel to sit until beginning to thicken but is still spoonable, about 20-30 minutes.