Imagine fudgy brownies without the chocolate and instead bursting with bright lemon flavor and creamy milky white chocolate. These are a lemon-lover's dream!
Combine chopped white chocolate and butter in a heatproof bowl and place it over a saucepan with barely simmering water. Stir until completely melted and smooth. Or, melt in the microwave at 50% power in short 20 second bursts with frequent stirring so that it doesn't burn. NOTE: You might find that the mixture will not melt smoothly as there is a high quantity of butter compared to white chocolate, and this depends on the quality of the white chocolate. It may look a bit separated but it will incorporate evenly when you add it to the egg mixture. Alternatively you can melt the chocolate with half of the butter first and then add the remaining melted butter separately to the egg mixture.
Combine eggs, sugar, lemon zest and salt in a large bowl and whisk vigorously until pale and thick. Mix in vanilla. Mix in warm melted white chocolate mixture.
Sift in flour and fold it in gently. Just before all of the flour is incorporated, fold in the chocolate chips.
Spread the batter evenly into prepared pan and bake for 20-25 minutes until the top is shiny and crackly. A skewer inserted into the center should come out mostly clean with a few sticky crumbs attached. Transfer to a wire rack to cool completely.
Make the glaze. You can make a sugar glaze or a creamy white chocolate glaze. For the sugar glaze, combine powdered sugar and lemon juice in a small bowl and whisk until smooth and glossy. It should be opaque but flowing with a drizzling consistency. You can add more or less lemon juice if you would like it thinner or thicker. To make the white chocolate glaze, melt chopped white chocolate over a double boiler until completely melted, then stir in the lemon juice until silky and smooth.
You can add the icing over the still warm brownies for a glazed effect or spread it on after they're cooled for a thicker icing. Let the icing set for 20 minutes before cutting into squares.