At the bakery, we like the combination of fresh blueberries and raspberries, but fresh blackberries could be included or substituted for one of the two here. When local berries are abundant in the summer, I’ll throw bags of them into the freezer for winter baking. Toss frozen berries in a bit of the flour once thawed to keep them from “bleeding” into the muffin batter. Now that I’m living in Maine, I’ve become a fan of the small local blueberries, which have a deep, intense flavor. I like to support local farms by using frozen Maine blueberries out of season. Look for Blue Ox or Alexander blueberries, which are sold year-round at supermarkets across the country. Or go to Blue-Zee Farm (bluezeefarm.com), my local source in Penobscot, Maine, to order one-, three-, and five-pound boxes shipped to your door.

1. Set a 3-quart (3-liter) storage container on the work surface.
2. In a large spouted measuring cup, whisk together the buttermilk, oil, eggs, lemon juice, and vanilla.
3. In the bowl of a stand mixer fitted with the paddle attachment, add the all-purpose flour, buckwheat flour, granulated sugar, baking powder, and salt. Toss together or mix on the lowest setting for 1 minute. With the mixer running on low speed, stream half of the buttermilk mixture into the bowl. Stop the mixer and scrape the sides, bottom, and the paddle to begin to incorporate any dry pockets. Return the mixer to low speed and stream in the remaining buttermilk mixture. Stop the mixer before the mixture is completely combined. The batter should still look lumpy, but there shouldn’t be any visible dry areas at this point. Remove the bowl from the mixer, scraping any batter from the paddle into the bowl.
4. Fold in the berries until just distributed. Transfer the mixture to the storage container. Refrigerate for at least 2 hours but ideally overnight.
5. Preheat the oven to 425°F (230°C). Line the cups of a large 6-cup muffin pan or a traditional 12-cup muffin pan with paper liners. Divide the batter evenly among the cups. Sprinkle with the oat topping, lemon sugar, or coarse sugar, if using.
6. Bake the muffins for 10 minutes. Then, without opening the door, lower the oven temperature to 350°F (175°C) and continue to bake until a skewer inserted in the center of the muffins comes out clean, 18 to 20 minutes more for the large muffins and about 15 minutes more for the traditional muffins.
7. Transfer to a wire rack. Let cool in the pan for about 10 minutes. Remove and serve warm or let cool completely on the rack.

223 — Cafe Treats

Oat Topping

Makes about 130 grams (4½ ounces / scant 1 cup)

1. Cut the butter into 1/4-inch (6 mm) cubes and return to the refrigerator.
2. In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, brown sugar, oats, and salt on the Stir setting until combined, about 30 seconds.
3. Add the butter and mix on medium speed until crumbly, 1 to 2 minutes. (The mixture should not come together into a single mass.)

Lemon Sugar

Makes 135 grams (about 4¾ ounces / 2/3 cup)

With a vegetable peeler, peel the zest from the lemon in strips, then scrape as much of the white pith off the zest as possible. Roughly chop the zest and put in a food processor with the sugar. Pulse until the zest is finely ground and incorporated, about 2 minutes.