Preheat your oven to 350°F (175°C). Line a 10cm x 20cm loaf pan with parchment paper, leaving some overhang for easy removal.
Melt the dark chocolate using a double boiler or in the microwave, stirring every 30 seconds to prevent burning.In a large mixing bowl, whisk together the yogurt, milk, and coconut sugar until well combined.
Pour the melted chocolate into the yogurt mixture and whisk until smooth.
Sift the wholemeal flour, cocoa powder, baking soda, and a pinch of salt into the wet mixture. Gently fold with a spatula until just combined.
Transfer the brownie batter to the prepared tin and smooth the top. Bake in the preheated oven for 35 minutes. The brownies will rise and then settle as they cool.
While the brownies are cooling, mix the cream cheese and liquid sweetener in a small bowl until smooth. Place the frosting in the fridge until ready to use.
Once the brownies are completely cool, remove them from the tin using the parchment paper overhang. Spread the cream cheese frosting evenly over the top of the brownies. For best results, refrigerate for an additional 30 minutes to set the frosting before slicing.
Slice the brownies with a sharp, clean knife and enjoy!