Step 1: In a medium saucepan, combine the unsweetened cocoa powder, granulated sugar, and a pinch of salt. Whisk these dry ingredients together thoroughly to break up any clumps.
Step 2: Gradually add about 1/2 cup of the whole milk to the dry ingredients, whisking continuously until a smooth, thick paste forms. This ensures a lump-free hot chocolate.
Step 3: Slowly pour in the remaining 1 1/2 cups of milk, whisking constantly. Place the saucepan over medium heat and bring the mixture to a gentle simmer, stirring frequently to prevent scorching. Do not allow it to boil vigorously.
Step 4: Once simmering, reduce the heat to low and add the finely chopped semi-sweet chocolate. Stir continuously until the chocolate is completely melted and smoothly incorporated into the milk mixture. Continue to cook, stirring occasionally, for another 2-3 minutes until the hot chocolate has thickened slightly and is wonderfully smooth and glossy.
Step 5: Remove the saucepan from the heat and stir in the vanilla extract. Whisk it in well to distribute its fragrant notes evenly.
Step 6: Taste the hot chocolate and adjust sweetness if desired. If you prefer a sweeter drink, add a tiny bit more sugar, stirring until fully dissolved.
Step 7: Ladle the hot chocolate into your favorite mugs. Serve immediately with your preferred toppings, such as a generous dollop of whipped cream, a handful of mini marshmallows, or a sprinkle of chocolate shavings.