Place the dark chocolate and butter in a heatproof bowl. Set the bowl over a pot of simmering hot water, but do not let the bowl touch the water in the pot. Let the chocolate and butter melt, stirring the mixture occasionally using a rubber spatula. Once the chocolate and butter has melted, remove the heatproof bowl and place it aside. Let the chocolate-butter mixture cool to lukewarm (the melted chocolate-butter mixture should not be too hot, otherwise it may cook the egg mixture later on).
Place the eggs, sugar and vanilla extract in a separate clean bowl. Using an electric mixer, beat the egg-sugar mixture on low speed for 1 minute, then increase the speed to high and continue beating for another 4 minutes, until the mixture is thick and pale in colour.
Lower the speed to low and add in the melted chocolate-butter mixture. Mix until fully incorporated.
Sift in the flour, baking powder and pinch of salt directly into the batter and fold in gently. Fold in the chopped plain chocolate. The batter will be watery. Place the bowl of cookie batter aside in a cool place for 10 to 15 minutes. The batter will thicken slightly.
Preheat the oven to 180 degrees Celsius. Line baking sheets with baking paper.
Scoop a tablespoonful of the batter and drop it gently on the baking sheet. Repeat, spacing the cookie batter about 2 inches (5 centimetre) apart.
Bake the cookies for 8 to 10 minutes until the top of the cookies are wrinkly. Transfer the baking sheets to cool on a wire rack for 5 minutes before transferring the cookies to a wire rack to cool completely.
These cookies taste good by themselves or you can serve them with a scoop of ice cream. Or – spread a layer of softened ice cream on a cookie, top with another cookie and freeze until the ice cream is firm – ice cream cookies!
Store the baked cookies for up to 5 days in an air-tight container.
NOTES
I still find the cookies a tad too sweet (even though I’ve already reduced the amount of sugar used from 250 grams to 180 grams). It is hard to go on to the third cookie because it’s simply sugar-overload! So, I’m gonna reduce the amount of sugar used to 150 grams the next time I baked it and omit the chopped plain chocolate.