Preheat oven to 170 degrees Celsius. Line a muffin / cupcake tin with muffin / cupcake liners. Set aside.
Sift cocoa powder into a small bowl to get rid of lumps.
Measure the cream in another small bowl. Heat it up until hot but not boiling in a microwave or place it in a pan of simmering hot water. Pour the cream over the cocoa powder and mix with a spoon until a paste is formed and no trace of cocoa powder is left. Set aside to cool slightly.
Place the butter and sugar in a mixing bowl and beat with an electric mixer on medium speed for 3 minutes. Scrape down the sides and beat for another 2 minutes on high speed until light, pale and creamy. Scrape down the sides. Add in the eggs one by one, beating on medium speed for 1 minute and scraping down the sides before adding the next egg. Beat in the vanilla, followed by the cocoa-cream paste until incorporated.
Sift the flour, baking powder and salt directly into the mixing bowl and beat on low speed just until incorporated. Add in the chocolate chips and fold in with a rubber spatula, scraping down the sides and the bottom of the bowl to ensure batter is well-mixed.
Divide the batter among the liners (mine is 1/4-cup of batter per liner) and bake for 18 to 23 minutes until a skewer inserted into the centre comes out clean. Remove the cakes from the tin onto a wire rack and let cool completely.
Store in an air-tight container at room temperature for 3 days. The cake will last longer if you store it in the fridge, but let it come to room temperature before serving.