Line a 40cm x 27cm x 2,5cm (16" x 11" x 1") baking tray with non-stick baking parchment, and pre-heat your oven to 225°C (440°F/gas mark 7).
Place the cooked sweet potato and cookie butter into the bowl of a large stand mixer fitted with a standard beater, and mix on the lowest speed for 5 mins.
Add the date sugar, and mix for a further 3-5 mins, until the sugar has dissolved.
Mix the coconut flour with the salt and baking powder, and then add to the mixer, and continue to mix for 2-3 mins, until the flour has been incorporated.
Mix the vanilla with the milk, and add to the mixer. Mix for another minute or so.
Add the macadamias, and mix for another 30-ish seconds, just until they’re evenly distributed.
Turn the blondie mix out onto the baking tray, and level off, making sure you get right into the corners.
Bake in the centre of the oven for 20 mins.
Remove from the oven, and leave for an hour to cool before removing from the tray.
Once fully cool, melt the chocolate and coconut oil in a bowl over a pan of hot water, then decorate the top of the blondies by swiftly drizzling the molten chocolate back and forth in a diagonal pattern.
Once the chocolate is set, cut into 24 squares, and enjoy!