Preheat your oven to 190C/180C Fan/375F and line two-four baking trays with parchment paper.
Mix together the unsalted butter and both granulated and light brown soft sugars until light and fluffy and thoroughly combined.
Gradually add in the beaten egg and vanilla bean extract and continue to beat till smooth.
Add the rolled oats, plain flour, bicarbonate of soda, and baking powder and mix until a thick paste/cookie dough is formed. (I used my KitchenAid with the paddle beater for all of this as it makes the ingredients distribute evenly.)
Add the milk chocolate chips to the mix and beat again.
Using an ice cream/cookie scoop, scoop the portions of cookie (I used a 5cm scoop) and then roll each one in your hand till a smooth ball is formed.
Place them on the tray (fairly far apart so they don't touch) and squish them slightly till they're about 1cm thick.
Bake the cookies in the oven for 10-12 minutes
Once baked, remove from the oven and allow to cool.