Preheat the oven to 350°F, and line an 8x8-inch baking pan with parchment paper.
Simmer an inch or two of water in a saucepan over medium heat. Set a large glass bowl on top of the pan, and add the chocolate and butter. Stir until the ingredients are fully melted and combined. Remove the bowl from the pan and let it cool slightly.
8 ounces semi-sweet baker’s chocolate, ¾ cup unsalted butter
In a separate large bowl, use an electric mixer to beat the sugar and eggs together until they begin to turn pale yellow in color. Add the vanilla, and mix just until combined.