Preheat oven to 350°F; line a 9x13-inch pan with parchment.
Combine flour and sugar in a food processor; pulse in cold butter until coarse crumbs form for shortbread.
Press firmly into pan bottom; bake 20-22 minutes until lightly golden and set aside.
Meanwhile, combine butter, brown sugar, honey, and cream in a medium saucepan for caramel.
Boil over medium, stirring constantly; once boiling, cook 5 minutes without stirring.
Off heat, stir in vanilla; pour hot caramel over baked shortbread.
Immediately sprinkle with flaky sea salt to taste.
Bake another 15 minutes until caramel bubbles.
Cool completely at room temperature at least 2 hours; refrigerate 1 hour before cutting into squares. Store airtight up to 1 week.