Focaccia with Onion Marmalade, Blue Cheese, & Walnuts

Focaccia Dough
¼ cup plus 2 tablespoons olive oil
1½ cups Sweet-and-Sour Onion Marmalade
¼ pound blue cheese (I use Gorgonzola, Peter recommends Danish Blue), crumbled or cut into ½-inch pieces
1 cup coarsely chopped walnuts

Shape and dimple the dough in a 12 by 17-inch sheet pan, using the 2 tablespoons olive oil for preparing the pan and the ¼ cup olive oil for dimpling the dough. Let the dough rise at room temperature for 2 to 3 hours, or until it fills the pan.
Preheat the oven to 500°F. When the focaccia is fully risen and ready to bake, gently spread the onion marmalade evenly over the surface. Evenly distribute the blue cheese over the onion marmalade and scatter the walnuts over the top.
Place the sheet pan on the middle shelf of the oven, lower the temperature to 450°F, and bake for 20 minutes. Rotate the pan 180 degrees and continue baking for 20 to 25 minutes longer, or until the dough is golden on the bottom and the top.
Remove the finished focaccia from the oven and immediately transfer it to a cooling rack. Drizzle any oil remaining in the pan over the top. Let cool for at least 20 minutes before cutting and serving.