Preheat the oven to 350°F (175°C).

Line the inside of a 9-inch square pan with 2 lengths of foil, positioning the sheets perpendicular to each other and allowing the excess to extend beyond the edges of the pan, or with a single large sheet of extra wide foil or parchment paper. Lightly butter the foil or parchment.

In a medium saucepan over low heat, melt the butter. Add the chocolate and stir until it is melted and smooth. Remove the pan from the heat and stir in the sugar and vanilla until combined. Beat in the eggs, 1 at a time. Add the flour and stir energetically for 1 full minute—time yourself—until the batter loses its graininess, becomes smooth and glossy, and pulls away a bit from the sides of the saucepan. Stir in the chocolate drops and the dried cranberries.

Scrape the batter into the prepared pan, sprinkle with chopped cocoa beans and bake until the centre feels almost set, about 30 minutes. Do not overbake.

Let the brownie cool completely in the pan—this is the difficult part—before lifting the foil or parchment and the block of brownie out of the pan. Cut the brownie into squares. (The brownies will keep well for up to 4 days and can be frozen for 1 month.)