In a large mixing bowl, vigorously whisk together the melted butter, dark brown sugar, and vanilla extract until completely smooth. Add the room-temperature egg and whisk for another 30 seconds until fully incorporated.

Sprinkle the blanched almond flour, baking soda, and fine salt over the wet ingredients. Use a silicone spatula to gently fold the mixture until a cohesive, slightly sticky dough forms.

Gently fold in the dark chocolate chunks, reserving a few for the tops. Cover the bowl with plastic wrap and chill the dough in the refrigerator for at least 30 minutes.

Preheat your oven to 350°F (175°C). Line a heavy-duty metal baking sheet with crinkled brown parchment paper. Scoop 1.5 tablespoon-sized mounds of dough, roll into balls, and place them two inches apart on the sheet. Press reserved chocolate chunks into the tops.

Bake for 10 to 12 minutes until you see golden-brown baked edges and a soft cracked surface in the center. Immediately sprinkle with flaky sea salt while hot. Let the cookies rest on the metal baking sheet for exactly 10 minutes before transferring to a wire rack.