Step 1Heat the oven to 325 degrees. Roughly chop the chocolate into pieces. Transfer to a medium-sized bowl and add the butter. Place the bowl over a saucepan of simmering water, until the two ingredients have melted. Mix well and transfer to a large bowl; set aside.
Step 2Sift the sugar and flour together, then stir into the chocolate. Add the eggs and mix well. Cover and let rest at room temperature for 30 minutes. The batter will thicken as it stands.
Step 3Spoon one-fourth cup batter into each paper-lined muffin cup. Bake 30 to 35 minutes. The brownies will still be moist when done; they will puff up and fall slightly as they cool.