Buckwheat Dough

1. Combine the flours and salt in a food processor. Pulse until combined. Add the cold, cubed butter and oregano. Pulse until coarse crumbs are formed. 
2. With the processor running, drizzle in the water. Continue to mix until the dough starts to pull away from the sides of the bowl. 
3. Immediately gather the dough and form it into an even, flat disk. Wrap the dough with plastic wrap and chill for 45 minutes (at this point, the dough can be stored in the fridge for up to 3 days). 

Crostata

1. Heat a 12” skillet over medium heat. Add enough olive oil to coat the bottom. Once hot, add the fennel and a pinch of salt. Cook for about 6-8 minutes or until soft and slightly caramelized, stirring often. Transfer the fennel to a plate. 
2. Add a little more olive oil to the skillet. Add the leeks and a pinch of salt. Cook for about 2 minutes. Transfer the leeks to the plate. Add a little more olive oil again. Add the chard and a pinch of salt. Squeeze in the juice of half of the lemon. Cook for just 30 seconds or until wilted. Turn off the heat. 
3. Preheat the oven to 425°F. Once the dough has finished chilling, allow it to sit at room temperature for a few minutes to slightly soften. Place the dough onto a lightly floured surface and sprinkle more flour over top. Use a rolling pin to gently roll the dough out (aim for a 12” circle). Carefully transfer the dough to a sheet pan lined with parchment paper. 
4. Distribute half of the cheddar over the dough, leaving a 1” edge. Continue to layer the chard, fennel, leeks, and remaining cheddar on top. Fold the dough over the vegetables around the edges, pressing any cracks together as needed. Brush the egg onto the edges. Sprinkle the edges with 1 tablespoon of sesame seeds. 
5. Bake the crostata for about 35 minutes, or until the edges are crisp and golden. Meanwhile, add the honey, oregano, 2 teaspoons of lemon juice, and remaining 2 teaspoons of sesame seeds to a small mixing bowl. Stir to combine. 
6. Cut the crostata into 6-8 slices. Serve with a drizzle of the honey mixture and a pinch of flaky sea salt over top.