Consider this recipe a template—you can substitute the mortadella with ham, salami, cooked bacon (or omit it altogether for a vegetarian version), swap the provolone for another cheese, use black olives in place of green (brined or oil-packed are both fine), add dried fruit or nuts, replace the scallions with chives. If you choose to use provolone, look for aged provolone, called provolone picante, which is sharp and salty; the sliced variety used for sandwiches doesn’t have a sufficiently assertive character.
Makes one 9x5-inch loaf
Unsalted butter, for greasing the pan
1¾ cups all-purpose flour
¼ cup finely chopped scallions (about 5)
2 teaspoons chopped fresh thyme leaves
1½ teaspoons baking powder
1 teaspoon kosher salt
½ teaspoon baking soda
½ teaspoon ground black pepper
Pinch red pepper flakes
½ cup buttermilk
½ cup extra-virgin olive oil
3 large eggs
4 ounces mortadella, diced into 1/3-inch cubes (1 cup)
3 ounces provolone piccante, grated (1½ cups)
½ cup coarsely chopped pitted green olives
Preheat the oven to 350F and arrange a rack in the center. Generously butter a 9x5-inch loaf pan and set aside.
In a large bowl, whisk together the flour, scallions, thyme, baking powder, salt, baking soda, pepper and red pepper flakes. In a separate medium bowl or measuring cup whisk together the buttermilk, olive oil, and eggs. Pour the wet ingredients into the dry and use a rubber spatula to combine. Fold in the mortadella, 1 cup of the grated provolone and the olives until well combined, then scrape the batter into the prepared pan and smooth the top. Sprinkle the remaining ½ cup provolone evenly over the top.
Transfer to the centered oven rack and bake until golden brown on top and a toothpick inserted in the center comes out clean, 55 minutes to 1 hour. Transfer to a wire rack and let cool for 10 minutes, then turn the loaf out of the pan and let cool completely. Because the cake contains a large amount of olive oil it will keep, well wrapped at room temperature, for up to 3 days, or can be sliced and frozen for longer storage (up to one month). Leftover slices are especially good toasted, or the bread can be cubed, toasted and used as croutons.