
James is very proud to have a pastry department at Blue Bottle Coffee. He loves that making our own food gives us control over the customer's entire experience. He has made a big deal about not having what he calls a PBM (perfunctory bran muffin) on his shelves. Well, it turns out that many people really like to have a muffin for breakfast, and customers who came in expecting to find one in the pastry case were disappointed that we didn't have anything resembling a muffin. Knowing full well that "muffin" is a euphemism for "cake for breakfast," I decided not to hide it—I developed a buttery, fruit-based cake that we serve in an elegant paper cup.
A buckle is a traditional American cake, essentially a coffee cake with fruit, usually blueberries. Legend has it that you're supposed to pile so much streusel on top of the cake that it buckles during baking, creating a ravine of fruit and streusel goodness through the center of the cake. I've never actually seen a buckle buckle, but when making this recipe at home, I like to bake it as one large cake, which increases the surface area (and, therefore, chances of buckling) and reassures James that it is a coffee cake, not a muffin.
Substitutions: The buckle allows us to showcase seasonal fruit in our pastry cases; for example, a traditional blueberry buckle with vanilla-almond streusel in the spring; a raspberry and peach buckle with lemon-pistachio streusel in the summer; pumpkin buckle with spiced walnut streusel in the autumn; or a roasted mandarin buckle with pecan streusel in the winter. Substitute an equal amount of any fruit for the strawberries. Substitute any nut for the pistachios, and add any type of citrus zest to the streusel. For a pumpkin buckle, substitute 3/4 cup pureed roasted pumpkin or other winter squash (see Note) for the fruit, and add 1/4 teaspoon each of ground nutmeg and cinnamon to the flour mixture when making the cake.
Note: To make pumpkin puree, preheat the oven to 375°F (190°C). Halve an edible variety of pumpkin or an acorn, kabocha, curry, or butternut squash and scoop out the seeds. Put the halves face down on an oiled baking sheet and bake for about 45 minutes, until the squash collapses and is easily pierced with a knife. Let cool until it can be handled safely, then scrape out the pulp. Mash or process in a food processor until smooth. For a quicker, if less distinguished puree, it's fine to use unsweetened canned pumpkin puree.

