Fill a medium pot with 1–2 inches of water and bring to a gentle boil. Reduce heat so the water simmers. Place a heatproof bowl or smaller pot that fits over the pot (without touching the water) and add 8 ounces unsweetened chocolate (chopped) and 2 tablespoons salted butter to the bowl.

Stir the chocolate and butter over the simmering water until fully melted and smooth. Remove the bowl from the heat and stir in 2/3 cup pure maple syrup. Let the chocolate mixture cool until warm but not hot (about 5–10 minutes).

In a large bowl, whisk 2 eggs until blended. Stir in 2 teaspoons pure vanilla extract.

In a separate bowl, whisk together 3/4 cup buckwheat flour, 2 teaspoons baking powder, and a pinch of fine sea salt.

Slowly add the warm chocolate-maple mixture to the eggs, stirring constantly to combine and to avoid cooking the eggs. Stir until smooth.

Add the dry flour mixture to the wet mixture and mix until just combined. Fold in 1/2 cup dark chocolate chips.

Cover the bowl with plastic wrap and refrigerate the dough until chilled and firm, about 1 hour (you can refrigerate overnight if preferred).

When ready to bake, preheat the oven to 350°F. Line a baking sheet with parchment paper or lightly grease it.

Scoop or roll portions of dough into balls (about 1–2 tablespoons each), place them on the prepared baking sheet about 2 inches apart, and gently press each ball to flatten into a cookie shape. Sprinkle the tops with coarse sea salt.

Bake for 8–10 minutes, until the edges have set and the centers are still slightly soft. Remove from the oven and let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to finish cooling.