First of all, you'll need to make some browned butter. This is really easy. Simply add your butter to a small pan and melt over a gentle heat. When the butter has all melted, turn the heat up to a medium and, stirring regularly with a silicon spatula, wait for the butter to turn from a pale yellow to a clear, bronze colour. You should see brown specks on the base of the pan. Allow the browned butter to cool to room temperature before you use it, around 15 minutes. In a stand mixer or large bowl, mix together your butter, caster sugar and egg and mix until smooth
Add the flour and baking powder and mix until combined.
Add in the chocolate chunks.
Cover and chill for a minimum of 2 hours. After around 1 hour 45 minutes, preheat your oven to 170ºC.
Place the extra sugar and cinnamon in a bowl and mix together.
Line your baking sheet(s) with greaseproof paper.
Take the dough out of the fridge and roll into walnut sized balls. They don't have to be exact but obviously if you roll larger balls, you'll get fewer cookies.
Roll each ball in the sugar and cinnamon mix and then place on a cookie sheet. I put 6 balls per sheet as they spread when baking.
Bake for 8 to 10 minutes. Each oven will vary so check on them after 8 minutes. They're baked when they're golden brown.
Allow to cool on the cookie sheet before moving.