Make the brown butter – this must be done at least 2 hours before but can be made up to 3 days before. Heat the butter in a saucepan over a moderate heat. Heat until it turns a medium brown colour. This will take 2 - 4 minutes depending on how hot your hob is and how your saucepan conducts heat. Keep your eye on it because it can change and burn quite quickly. When it is brown, pour into a small bowl and leave to cool. When cool, put in the fridge to solidify. 

Make your cookies: start making the actual cookies at least 40 – 45 minutes before you want to cook them. You need 10 minutes to allow the brown butter to soften a little after being in the fridge.  Plus, the mixture is very soft and, ideally, you need time to chill the dough for a minimum of 30 minutes in the fridge or 15 minutes in the freezer.

Put the butter, salt and both of the sugars into a large bowl and using an electric whisk mix until fluffy. This should take 3-4 minutes. 

Add the egg and vanilla extract/paste and continue to whisk until thoroughly mixed.

Add the flour and baking powder to the butter mixture and beat, on a slow speed, until almost entirely incorporated. Alternatively, fold in by hand.

Fold in the chocolate chunks and walnut pieces until evenly mixed throughout. The dough will be quite soft and sticky at this stage. (NB hold a few chunks of chocolate and walnut pieces back, just 2-3 of each, to add into the last cookie.)

Divide the dough into rough balls, (I use 30g/1 large tablespoon of dough per cookie) and place them, close together on a baking sheet lined with baking parchment. Roll gently into a neater shape and then stick on the toppings. Cover with cling film and put in the fridge for a minimum of 30 minutes (or the freezer for a minimum of 15 minutes) to harden a little.

NB You should get around 25 dough balls - this will depend on how accurate you are measuring them out and how much of the cookie dough you eat as you prepare them!

Five minutes before you want to cook your cookies, preheat oven to Fan Oven 160°C /180°C/350°F/Gas 4 and line several sheets with baking parchment.

Place the cookie dough balls spread out on baking sheets. Depending on the size of your baking sheet, I cook between 4 - 6 at a time.

Baking one tray at a time: bake for 10 - 12 minutes.( I cook mine for 1 minute.)

Baking two trays at a time: add one minute to the total time to cook. Bake for half this time and then quickly swap the trays over i.e. put the top tray on the lower shelf and the tray from the lower shelf and on the higher shelf and cook for the remaining time.

(So for one tray I cook for 11 minutes and 2 trays for 6 minutes, swap the trays and then another 6 minutes = 12 minutes on total.)  

The cookies are cooked when: they have spread out, are starting to brown on the edges and look ever so slightly underdone. They should still be soft in the middle. Let them cool on the baking sheet for 10 minutes and then transfer to a cooling rack.