- To brown the butter: In a small saucepan over medium high heat, melt butter. Whisk continuously and be careful not to let it burn. Let the butter boil until it foams up, and then turns brown and has a nutty aroma.
- As soon as you see the butter has turned brown, remove it from the heat and pour it into the bowl of an electric mixer. Let the butter come back to room temperature.
- When the butter is cool, add dark brown sugar and granulated sugar and mix on medium speed. Then add the egg, and egg yolk. Mix until creamy. Add in the vanilla extract, and mix. Add creamy peanut butter and mix on low speed until well combined. Add the oil and Greek-Styled yoghurt and mix until combined.
- In a separate small bowl, mix together flour, salt and baking soda. Gradually add the flour mixture into the peanut butter mixture on low speed until it is well combined and a dough has formed.
- Wrap the dough in plastic wrap, and chill in the fridge for a couple of hours.
- Preheat oven to 180°C.
- With a large scoop (ice cream scoop size), scoop balls of chilled dough onto a Silpat lined baking sheet, six per batch. Press down dough with the tines of a fork to make a crosshatch pattern, and sprinkle with sparkling sugar. Bake for 11-13 minutes. The edges should be slightly golden.
- Cool on the baking sheet for a few minutes before moving to a cooling rack.