Preheat the oven to 180C. Line 2 cookie trays with baking parchment.
Melt the chocolate and butter in a heatproof bowl {in the microwave or over a double boiler}, whisk until smooth, then stir in the cocoa powder.
Place egg, yogurt and brown sugar in bowl of stand mixer, and whisk at high speed for 1 minute. Beat in vanilla extract, salt and baking soda, followed by the melted chocolate mix.
Fold in oats, whole wheat flour and butterscotch chips on the lowest speed until just combined.
Allow to stand for 5 minutes for oats to absorb moisture. {If the dough feels a little 'loose', add an extra spoon or two of oats.}
Scoop out dough with cookie scoop or drop spoonfuls on a tray, shaping as you go, at least an inch apart. Flatten with the tines of a fork.
Bake for approximately 20 minutes until the top feels set for a soft fudgy cookie, {I use the KitchenAid cookie tray for baking chocolate chip cookies, and the lower element only in my oven}
Leave to cool on tray for 5-10 minutes, then transfer to cooling rack to cool completely.
Store in a cool place.