Preheat oven to 375F.
Line bottoms of muffin tins with parchment paper and lightly grease. Or spray with Baker's Joy Baking Spray.
In a small, microwave-safe bowl, melt together chocolate chips and butter, stirring with a fork until very smooth.
Pour warm chocolate mixture into a medium mixing bowl with sugar. Whisk to combine. Beat in eggs one at a time, waiting until each has been fully incorporated to add the next, then mix in vanilla extract. Sift cocoa powder into the bowl and whisk until well-combined.
Pour into prepared muffin tins.
Bake for 17 minutes.
Allow cakes to cool in the pan for 5 minutes, then run a knife around the edge of the cakes and invert onto a bakers rack.
Make the glaze:
Melt the chocolate and butter in the microwave on high in 1 minute increments, stirring with a rubber spatula until smooth.
Pour the warm glaze over the cooled cakes using an offset spatula to spread the glaze evenly over the edges and around the sides of the cakes.
Refrigerate the cakes until the glaze is set. Before serving bring the cakes to room temperature.