Reduce champagne: Pour the champagne into a small saucepan. Bring to a boil, reduce the heat to medium and simmer until reduced down to ¼ cup, about 8-10 minutes. Let cool completely at room temperature.
Chop the chocolate very finely and place it in a bowl.
Heat the cream in a small saucepan until almost steaming, don't let it simmer or boil. Pour over the chocolate and let stand for 2 minutes.
Stir slowly with a rubber spatula until the ganache is perfectly smooth.
Add butter and 4-5 tablespoons champagne, stir to combine.
Let cool slowly at room temperature. When completely cool, cover with plastic foil and refrigerate for at least 3-4 hours or until firm. I prefer to leave it overnight.
Color sugar: Place the sugar in a zip-lock freezer bag. Add a few drops of food coloring. Close the bag well and knead the color into the sugar. Add more food coloring if you find it necessary.
Place the colored sugar on a large plate.
Form the truffles:
Roll truffles: Scoop small amounts of ganache with a teaspoon and roll the truffles; they should be about the size of a smaller walnut; you will have about 30.
Coat with sugar: Wash your hands with water every 4-5 balls or so. Once all the truffles are ready, roll them into the colored sugar.
Keep refrigerated in airtight containers. They will keep for at least 2 weeks.
I recommend using a digital kitchen scale for measuring the ingredients, measuring chopped chocolate in a cup will probably be way off and the ratio of chocolate to cream is important for this recipe. (Amazon affiliate link)
I had dark chocolate with 70% cocoa and the balls were heavy on the chocolate taste and slightly bitter. The higher the cocoa percentage, the more pronounced the bitterness. Go as high as you like it. You can also go a bit lower and use dark chocolate with 60% cocoa. The bitter notes will be milder. However, I would not go much lower than that, chocolate with less than 50% cocoa is milk chocolate. Chocolate chips are not suitable for this recipe.
You might have some leftovers, keep them in a jar in the pantry. Alternatively, roll the truffles in pure cocoa powder, desiccated coconut, ground nuts, or shiny sprinkles.