The original recipe said it should take 20 to 30 minutes at a slightly-higher oven temperature. Mine took about twice that long, but I baked it a lower temperature since I was concerned about overcooking the white chocolate. Note that this is a recipe more about technique than one to be followed strictly to the letter. So if you think your batch is done before the time indicated, then it’s likely done. Basically what you’re doing is checking the chocolate every ten minutes and giving it a good stir to promote the caramelization. The only danger is overcooking: you want to cook it until it’s the color of natural peanut butter. If you do overcook it and it gets grainy, you can press it through a fine mesh sieve and it’ll be just fine. Update: Because of variations in white chocolate, if you’d like to ensure that the white chocolate will melt more smoothly, add 1 or 2 tablespoons of unflavored vegetable oil or cocoa butter (not regular butter), to the white chocolate at the beginning of the process.