Salted brown butter biscuits

I spent all christmas calling these salted caramel biscuits. Turns out I was wrong. Maybe it was all the butter going to my head - because I just can't stop eating these biscuits... which is okay because they cover about 1 food group - dairy, oh and energy (is that a food group?). Recipe found by chance from here: Best biscuits ever.

Here is the recipe as modified by me.
Ingredients
250 grams unsalted butter
130 grams dark brown sugar
2 teaspoons pure vanilla bean paste
350 grams plain flour
2 teaspoons Fleur de Sel de Guérande or Murray River Salt

Instructions
Preheat the oven to 180℃.  Line 2 large baking sheets with baking paper.  

Cut the butter into pieces and Place butter in a saucepan over a low heat.  Melt the butter and cook until it starts to brown and gives off a warm, nutty aroma.  Stir from time to time to make sure the butter browns evenly.  Remove from the heat and pour into a large bowl.   Set aside to cool slightly and then refrigerate until it starts to set again but is not too firm.  

Add the sugar and vanilla to the browned butter and whisk or beat until very light and fluffy and the sugar is dissolved.

Finally, add the flour and salt and mix to form a soft dough. Refrigerate for 30 minutes (don't go any longer - I did and ended up with cement like discs)

Roll out the pastry to about 4mm thickness and cut into cookies using your favourite cookie cutter. Place the cookies on the baking sheets and refrigerate for 30 minutes.  Prior to baking, lightly sprinkle a little extra Fleur de Sel de Guérande or other salt on each cookie.  You can lightly press the salt into the cookie to make sure it adheres to the dough properly but do this gently.   Bake the cookies for about 10 – 12 minutes.  You may need to rotate the sheets half way through baking to make sure they brown evenly.  They will be a golden colour when cooked. Remove from the oven and leave the cookies to cool on the baking sheet for about 10 minutes before transferring to a wire rack to cool completely.   Store in an airtight container.