Preheat the oven to 180C/350F. Line an 8 x 8-inch pan with parchment paper.
In a microwave-safe bowl, add the chocolate and butter and microwave in 30-second intervals until the butter has melted. Whisk together with the chocolate until smooth.
Add the sugar then the eggs, one at a time, until combined, then stir through the cocoa powder until smooth.
Transfer the batter into the lined pan and bake for 25-27 minutes, or until a skewer comes out mostly clean.
Let the brownies cool completely, before spreading the frosting on top. Top with candy buttons and slice and serve.
Notes
For a vegan option, use dairy free chocolate, dairy free butter and vegan candy buttons.For a keto option, use sugar free chocolate and a brown sugar substitute. TO STORE: Leftovers can be stored at room temperature, covered, for up to five days. If you'd like these brownies to keep longer, store them in the refrigerator. TO FREEZE: Place the baked and frosted brownies in an airtight container and store them in the freezer for up to 6 months.