First, brown 120g of the butter & leave to cool to room temperature. Weigh your butter once browned, there should be 100g. Leave to firm up in the fridge for 30 minutes - 1 hour. Whilst your brown butter is cooling, chop the remaining 80g of butter into even pieces & leave to soften at room temperature.
Place the raisins into a bowl & cover with boiling water. Leave to soak for 10 minutes then leave to drain whilst you make the cookie dough.
Into the bowl of a stand mixer, place the brown butter, the softened butter & both of the sugars. Use the paddle attachment to mix together until fully combined (make sure not to overmix the butter at this stage, 2-3 minutes of mixing maximum).
Beat the egg, yolks & vanilla together then with the mixer running on a medium speed gradually beat into the butter & sugar.
Sift together the flour, cinnamon, baking powder, bicarbonate of soda & salt.In a jug blender, blitz the porridge oats into a coarse flour (will take around 10 seconds on a high speed).Add the oats & flour mix into the butter & egg & mix on a low speed until just combined. Roughly chop 60g of the chocolate & mix into the cookie dough along with the raisins. Chill the dough in the fridge for 30 minutes to firm up.
In the meantime, chop the remaining chocolate into 15 equally sized chunks.
Once the dough has firmed up, scoop into 15, 75g portions & roll into balls with your hands. Making sure that there’s plenty of chocolate & raisins in each portion. Press a dark chocolate chunk into the top of each ball.Place the portioned cookie dough on a baking tray or into a large container then leave in the fridge overnight. The next day, preheat an oven to 180°c.Take the cookies out of the fridge & leave to warm up slightly while your oven is preheating. Line 3 large baking trays with baking parchment & place 5 cookies on each tray, making sure there’s plenty of room between them.For best results, bake the cookies one tray at a time. Bake the cookies for 13-14 minutes, until the cookies are set & golden brown round the edges.Using a large, round cookie cutter, scoot each cookie into a perfect round shape. Sprinkle each cookie lightly with Maldon salt, then leave to cool completely.