Preheat your oven to 350°. Line a 9x13 baking tray with parchment paper or brush it really well with butter.
Melt the butter in a saucepan over medium heat, stirring often, until the butter foams, then browns, about 5–10 minutes. Transfer brown butter to a large mixing bowl; let cool slightly.
Whisk the brown sugar and vanilla into the brown butter. Continue whisking until thoroughly combined then add in the eggs one at a time. Next, switch to a rubber spatula and fold in the flour, followed by the chocolate chips and toasted coconut.*Optional: reserve a small handful of chocolate chips and coconut flakes then sprinkle them on top of the blondies during the last five minutes of baking.
Bake until golden brown and firm 20-25 minutes. As soon as they come out of the oven, sprinkle with sea salt. Let cool completely before serving, or at least try to!
Notes
Store tightly wrapped at room temperature. Blondies will stay fresh for up to 3 days.