Place sliced butter into a light-coloured pan or skillet. Melt over medium-high heat, stirring continuously, until becomes foamy, then turns clear and starts showing brown specks. You'll also notice nutty aroma. It's done after approx. 5 min, at medium brown stage. Transfer it to a large bowl and allow to cool.
In a separate bowl sift both flours and mix in baking powder and salt using a whisk.
Once the butter has cooled a little bit, add sugar and orange zest to it and mix it with a whisk for a minute, just to combine. Then add eggs, one at the time, with vanilla extract and whisk for a minute until combined.
Add dry ingredients in two batches and combine with a wooden spoon to form a dough. (You can do this in a stand mixer, with a paddle attachment). Add candied orange peel and chopped chocolate disks, leaving 30 disks for later.
Form 80 g balls, put a chocolate disk in the middle of each ball of dough and then stick one on top. Put cookie dough balls on a baking tray, cover with plastic wrap and chill for a couple of hours or up to 3 days before baking.
Preheat the oven to 190˚C or 375˚F. Line two baking sheets with baking paper. Leave 2-3 inches (5-8 cm) between each cookie dough ball and bake for approx. 12-15 min. It depends on your oven.* When done, cookies should be golden and crispy outside but soft to the touch. Leave them on a baking tray for 2-3 minutes to firm up a little bit before transferring to a cooling rack to cool completely.
1. You can freeze cookie dough balls and bake them later, just add a couple of minutes more when baking. I suggest freezing the cookie dough balls on a baking tray and then transferring them to a ziplock bag, so you can easily remove just a couple when you get that cookie craving. :)2. You can use dark chocolate discs instead. I used Belcolade belgian chocolate. If you can't find any, try to use the best quality chocolate bar you can and roughly chop it. *3. Not all ovens are the same. I suggest you bake one cookie dough ball as a "test" batch to see how you like them and if you should bake them longer or shorter. When in doubt, always go for the shorter amount of time - that way you won't overbake them and you'll get that soft and gooey center.