Line an 8x8 inch baking dish with parchment paper, leaving an overhang on two sides for easy removal later. Remove the Greek yogurt from the refrigerator and let it sit at room temperature for about 15-20 minutes until it reaches approximately 70°F—this is crucial because cold yogurt will cause the melted chocolate to seize and become grainy. While the yogurt warms, measure out your chocolate chips.

Place the dark chocolate chips in a microwave-safe bowl and heat in 15-30 second intervals, stirring between each interval, until the chocolate is completely smooth and melted. I find that stopping just before the chocolate looks fully melted and letting residual heat finish the job prevents overheating and keeps the texture silky. This usually takes 45-60 seconds total depending on your microwave's power.

Working quickly while the chocolate is still hot, add the room-temperature Greek yogurt to the melted chocolate and stir vigorously until the mixture is completely smooth and well combined. The heat from the chocolate will warm the yogurt and create a creamy, fudgy texture. Mix for about 30-45 seconds until no streaks of yogurt remain—this swift combination is what gives the fudge its signature dense, creamy consistency.

Pour the chocolate-yogurt mixture into the prepared pan from Step 1 and use an offset spatula or the back of a spoon to smooth the top into an even layer. Place the pan in the refrigerator and chill for at least 4 hours, or preferably overnight, until the fudge is completely firm and set. Once firm, lift the fudge out using the parchment paper overhang, cut into 1-inch squares with a sharp knife (wiping the knife between cuts for clean edges), and serve at room temperature or chilled.