Hey, I've had sucess following this recipe from finecooking.com, but I decided to swap the 5 Oz semisweet + 2 Oz of bittersweet chocolate for 7 Oz of White Chocolate. I melted the chocolate with the butter and it was all good. It only started to seperate when I whisked in the sugar. The blob of white chocolate was in a pool of melted butter. There's some science involved, I'm sure, but I'm clear about it. What I understand is that White Chocolate cannot be easily interchanged with recipes. I may have overheated the white chocolate or moisture(from the whisk) may have acidentally be incorporated. Has my chocolate seized? Causing it to seperate from the butter? Fudgy Brownies 5 oz. (10 Tbs.) unsalted butter, at room temperature 2 oz. unsweetened chocolate 5 oz. bittersweet chocolate 1 cup sugar 2 tsp. vanilla extract Pinch salt 2 large eggs, at room temperature 1 large egg yolk, at room temperature 3 oz. (2/3 cup) all-purpose flour.