Mixed Greens Galette with Caramelized Onions & Goat Cheese

1. Up to 3 days in advance, make the dough: In a food processor or large bowl, pulse or whisk together flour, cornmeal and salt. Add butter and pulse or cut with a pastry
cutter until butter is in tiny pieces, 15 1-second pulses. Add 5 tbsp buttermilk and pulse or stir with a spatula until dough just comes together. Pour out onto a lightly floured surface and knead a few times until mixture becomes a cohesive dough. Form dough into an 8-inch disk, wrap in plastic, and refrigerate for at least 2 hours and up to 3 days.

2. Up to 3 days in advance, make filling: In a large heavy-bottomed saucepan on medium, melt butter. Add onions and stir to coat. Cook, stirring occasionally, until onions begin to soften, 8 minutes. (Note: If onions are beginning to color, reduce heat to medium-low.) Sprinkle with ¼ tsp salt and stir to combine. Continue cooking, stirring occasionally, until onions are very soft and just beginning to stick to bottom of pan, 10 minutes more. Add vinegar and 2 tbsp water and continue cooking, stirring occasionally, until onions are very soft and browned, 5 minutes more. Add greens and continue cooking, stirring gently, until greens are wilted, 2 to 3 minutes. Remove from heat and stir in remaining ¾ tsp
salt and pepper. Transfer to a heat-proof bowl and cool completely.Once cooled, stir in goat cheese and 1/3 cup Manchego cheese. Store in an airtight container in the fridge.

3. Up to 1 day before serving, assemble galette: Remove dough from refrigerator for 10 minutes before rolling. On a sheet of parchment paper dusted with flour, roll dough out into a 13-inch round, rotating the dough as you roll to make sure it’s not sticking. Transfer parchment paper with dough to a large baking sheet.

4. Spread filling mixture over galette, leaving a 2-inch border. Fold edges up around filling. Wrap tightly with plastic wrap and return to refrigerator.

5. 1 hour before serving, preheat oven to 400°F.

6. 30 minutes before serving, bake the galette: Remove galette from refrigerator and brush top of crust with remaining 2 tsp buttermilk. Sprinkle remaining 1/3 cup Manchego cheese over the filling. Bake until crust is golden brown, about 25 minutes.