Place rack in the middle of the oven and preheat to 350. Lightly butter the bottom and sides of a 12 x 17" rimmed baking sheet and line with parchment leaving an overhang on two opposite sides of the pan.

In a large bowl use your hands or a fork to combine the flour, brown sugar and salt. Slowly drizzzle in the melted butter and stir with a fork until it looks moist and crumbly. Using your hands or fork, press the dough evenly over the bottom and up the sides on the baking sheet. Refrigerate for 15 minutes to set the crust.

Line the crust with parchment and fill with dried beans, rice or pie weights.. Bake for 12-15 minutes or until crust is set and lightly browned. Remove parchment and weights and set the crust on a wire rack to cool completely before filling.

Filling:

In a large skillet or saucepan melt the butter over medium-high heat, stirring with a heatproof spatula. Stir up the brown bits so they don't burn. The butter will begin to foam up. Continue cooking over medium heat until the butter turns golden. Butter will sputter but as soon as it smells nutty and irresistable and becomes quiet, remove from heat.

Scrape it and the brown bits into a large heatproof bowl. Let cool about 15 minutes.

Whisk the sugar, honey, cornmeal and sea salt into the browned butter. Add the beaten eggs and yolks, slowly whisking until everything is fully combined. Whisk in the cane syrup, cream, vanilla and vinegar, in that order until smooth.

Pour the filling into the baked crust. Bake for 40-45 minutes until the edges of the filling have puffed up and the center only wobbles slightly if jiggled.

Remove from oven and sprinkle with the flaky sea salt. Let cool on a wire rack for at least 3 hours before cutting into bars.

Store at room temperature for up to 3 days or longer.