Preheat an oven to 180c (350f) and prep a parchment paper-lined 9 by 9 baking pan.
In a medium mixing bowl, add the butter and the white chocolate. Melt completely in the microwave or on a bain Marie. Let the chocolate mixture cool completely.
Add the sugar, lemon zest, lemon juice, oil, eggs, vanilla extract, and kosher salt, and mix until well combined.
Add the flour and mix until just combined and there are no lumps of flour visible. Don't overmix!
Pour the batter into a parchment paper-lined 9 by 9 inch square baking pan and bake in a preheated oven for 20-30 minutes or until the tops of the brownies are crinkly and a toothpick inserted into the brownie comes out with some moist crumbs.
Let the brownies cool for 1 hour before slicing, so they won't crumble and fall apart.
Make an easy lemon glaze. In a small mixing bowl, add powdered sugar, lemon juice, lemon zest, and milk, and mix until well combined. If the glaze is too thick, add an additional drop or two of milk.
If your glaze is too thin, add more powdered sugar until you get the right texture.
Top the cooled brownies with the glaze and spread it evenly with a spoon or an offset spatula. Slice, and serve!
Notes
Use room temperature ingredients. It is important that you use room-temperature ingredients like eggs and butter. This step ensures that your mixture mixes into a homogenous mixture and bakes perfectly. you don’t want to place cold batter into the oven.
Don’t overmix the batter, you don’t want to develop the gluten in the flour. This step ensures you have moist brownies and not dense and dry brownies.
Use fresh lemons for the best flavor. Zesting and juicing fresh lemons will give your brownies a bright, citrusy taste that you just can't achieve with bottled lemon juice.
Measure your flour correctly! When measuring your flour, avoid scooping it with a measuring cup. Instead, stir the flour with a spoon to create as many air pockets as possible, and spoon it into your measuring cup. Finally, level it with the back of a knife.
Be patient! I know it’s extremely tempting to eat brownies as they are pulled out of the oven, but let the brownies cool for at least an hour so they will be firmer and won’t crumble up.
Don’t overbake your brownies! To have super moist brownies, we like to underbake the brownies a little bit. Brownies continue cooking in the cooling process.
Ensure you line your baking pan with parchment paper to prevent the brownies from sticking to the pan.