Preheat the oven to 350F (177C) convection OR 325F (163C) conventional and line two cookie sheets with parchment paper.

In a small pot, over medium heat, cook the butter for 5-10 minutes, stirring intermittently until it begins to bubble and foam.*

Then stir continuously until you see the milk solids browning and settling on the bottom. Pour the butter into a bowl and allow it cool for a few minutes. 

Place the sugars into a medium-large bowl and zest the lemons on top. Use your fingers to run the zest into the sugar, allowing it to release it’s oils for flavor.

Add the hot butter and stir a little to cool the butter. Then add the egg, vanilla and lemon juice and whisk together aggressively for 2-3 minutes, until it's smooth and has lightened in color.**

Add the flour, cornstarch, salt and baking soda and fold the cookie dough just until there are a few streaks left of flour.

Fold in the chopped white chocolate, just until they're evenly dispersed.

Split cookie dough into 8 cookies (2.5 ounces each), (4-6 per cookie sheet, they spread a lot) and bake one sheet on the middle rack for 10 minutes, just until the edges are starting to brown.

Remove them from the oven, give the pan a quick tap on the counter and use a round biscuit cutter to scoot them around so they’re perfectly round. Return to the oven for 2-3 more minutes and repeat. The edges should be lightly browned and the top no longer wet.

Sprinkle with flakey sea salt and allow them to rest for at least 10 minutes on the pan before transferring off the cookie sheet.