9 Tbsp unsalted butter, cold from the fridge is fine (130g)
1/3 cup granulated sugar (80g)
1/3 cup brown sugar, light or dark is fine (80g)
1/2 cup smooth peanut butter, not natural (130g)
1 large egg (50g not including the shell), at room temperature
1 tsp vanilla bean paste or extract
1 1/4 cups All-Purpose Flour (155g)
1/2 tsp kosher salt (3g)
1/2 tsp baking soda
Turbinado / demerara sugar for rolling the cookies (alternatively use more granulated sugar or leave them plain)
Preheat the oven to 325°F (165°C).
Line two sheet pans with parchment paper.
Place the butter in a medium saucepan, and place over medium heat.
Cook until the butter has melted, then continue cooking, stirring with a whisk, until the butter foams and turns golden brown and nutty - this should take about 3-4 minutes.
Turn the heat down if you are worried it is going too fast - a good way to know that it is getting close is that it will start making much less noise as the butter boils.
Weigh out 7 Tbsp (100g) of the brown butter into a medium bowl and leave it to sit for 10-15 minutes so that it does not scramble your eggs.
To speed up this process, swirl the bowl often, or you can place the bowl in a larger bowl of cold water and whisk the butter frequently until it cools.
Add the granulated sugar, brown sugar, peanut butter, egg, and vanilla to the bowl.
Mix using an electric hand mixer or a whisk (or you can do this using the paddle attachment in a stand mixer) until the mixture has thickened and lightened in colour.
Add the flour, salt, and baking soda, and mix until just combined.
Place the sugar you are using to roll the cookies into a small bowl.
Using a size #40 cookie scoop, scoop 1 1/4 oz (35g) balls of dough onto the prepared baking sheets.
Roll each ball of dough between your palms to shape it into a ball, then roll each ball in the sugar (You might find it easiest to pop it into the bowl and shake the bowl to cover evenly).
Arrange the cookies on the baking sheet - you can usually fit 12 per sheet but if you want to divide them evenly then that works too.
Using a fork, press a criss-cross pattern into the tops of the cookies.
This will compress them slightly - you shouldn't have to push super hard.
Once you have pressed the fork into the cookies, either use your fingers to make the cookies into an even disc shape that is slightly thicker than the pressed down cookie, or use the 'scoot' - use a cookie cutter or something else round slightly larger than the cookie and swirl it around the cookie to make a nice even puck of cookie dough.
Bake the cookies for 12-13 minutes (one pan at a time), until the edges are set and are lightly golden brown.
They may still look a little under done in the middles - this is fine.
Remove the cookies from the oven and, if desired, use a cookie cutter slightly larger than the cookie to 'scoot' them into a perfectly round shape.
Leave the cookies to cool on the pan for 10 minutes, then transfer to a wire rack to cool completely.
Store cookies at room temperature in an airtight container for up to a week.