Chocolate-Cherry Focaccia

Combine 2 1/4 cups water, yeast, and 2 teaspoons granulated sugar in bowl of a stand mixer fitted with the dough hook attachment; whisk by hand until combined. Let mixture stand until foamy, about 5 minutes. Meanwhile, whisk together flour, cocoa, kosher salt, and remaining 1/3 cup granulated sugar in a medium bowl. Set aside.

With mixer running on low speed, gradually add flour mixture to yeast mixture, beating until all dry ingredients are combined, about 1 minute. Increase mixer speed to medium, and beat until dough is smooth and elastic and releases from sides of bowl, 10 to 12 minutes. Turn dough out onto a lightly oiled work surface; using oiled hands, stretch dough into a 10-inch square. (Dough will be sticky.) Sprinkle dough evenly with cherries and 6 ounces (about 1 1/2 cups) chocolate. Knead by hand until cherries and chocolate are evenly incorporated, about 30 seconds. Let stand 5 minutes to allow gluten to relax. Using oiled hands, stretch dough into a 15- x 10-inch rectangle. Fold in half lengthwise, and then fold in half crosswise to form a 7 1/2- x 5-inch rectangle. Let rest 5 minutes.

Coat a 17- x 12-inch rimmed baking sheet with 1/3 cup oil. Place dough on baking sheet, and stretch dough to fit inside with even thickness, pressing with fingers so dough fits into all corners. If dough springs back, cover and let rest 15 minutes, and stretch again.

Cover dough loosely with plastic wrap. Let stand at room temperature until bubbly and tripled in volume, 1 hour and 30 minutes to 2 hours. Alternatively, dough may be chilled overnight (12 hours); if dough is chilled more than 2 hours, let stand at room temperature 30 minutes before baking. During final 30 minutes of proofing time, place an oven rack in lower third position in oven, and place a pizza stone (or inverted baking sheet) on oven rack. Preheat oven to 425°F.

Uncover dough. Using lightly oiled fingertips, press indentions all across surface of dough, being sure to press down any cherries on surface. Arrange rosemary sprigs on top, if using. Pour remaining 1/3 cup oil evenly over top. Sprinkle evenly with turbinado sugar and flaky sea salt.

Place baking sheet with focaccia on hot pizza stone in preheated oven. Bake until bread is lightly browned and a thermometer inserted in center of focaccia registers at least 200°F, 20 to 22 minutes. Transfer baking sheet to a wire rack, and let focaccia cool 20 minutes. Using a fish spatula, release focaccia from baking sheet, and transfer to wire rack. Arrange remaining 1 ounce (about 1/4 cup) chopped chocolate over focaccia to melt partially from residual heat. Dust with powdered sugar, and serve alongside cherry balsamic vinegar and additional oil for dipping.