Preheat oven to 170°C fan-forced. Spray or line a muffin tin.
In a large bowl, whisk together the brown sugar, white sugar and eggs really well.
Add the oil (or melted butter) and Greek yoghurt (or sour cream). Mix to combine.
Dissolve the instant coffee in the hot water, then add to the bowl and mix through.
Add the cocoa powder, self-raising flour and salt. Whisk until mostly combined, then switch to a spatula to scrape down the sides and gently finish mixing. Don’t overmix.
Fold through the chocolate chips.
Divide the batter between the muffin holes. This makes 6 large bakery-style muffins.
Bake for 25 minutes, or until a skewer inserted into the centre comes out clean.
For regular-sized muffins or mini .muffins, bake for 18–20 minutes.
