Preheat the oven to 350 F. Line an 8x8 square pan (metal) with parchment paper - I use two small sheets and overlay them so all sides are covered.

Set the butter in a microwave safe bowl and heat to melt (45-60 seconds should do it). Add in the sugar and whisk then return it to the microwave for another 30-45 seconds. Whisk really well until the mix looks almost smooth.

Add the black cocoa and whisk to just combine, then heat again - this time for just 30 seconds. Whisk until the mix starts to look like it’s separating. Let cool briefly.

Add the eggs and immediately whisk very well, the batter should turn runny, smooth and cohesive. Whisk in the flour.

Pour the batter into the prepared pan. Add the white chocolate on top and then use a rubber spatula to gently bury it into the top half of the batter (we do this because white chocolate has a tendency to brown or caramelize if left uncovered while baking, and this batter is quite thin so the chips can sink to the bottom if we mix them in earlier).

Bake the brownies until the center puffs up, about 25-30 minutes. Let cool on the counter before slicing.

Store leftovers in an airtight container. For longer than 1-2 days of storage the brownies can be frozen and taken out to thaw before eating.