All the best parts of a muffin—no bottoms required.

This generous sheet-pan version delivers the golden, tender tops and juicy berry pockets of classic muffins in an easy, shareable format. It is perfect for breakfast, brunch, or an anytime treat, especially when blackberries are in season.

The sourdough discard adds a little depth without making the bake taste sour, while sour cream keeps every square soft and tender. For an easy bakery-style topping, use the streusel from Mama’s Freezer Streusel Bucket recipe; it is the perfect make-ahead topping to keep on hand. Or leave this bake plain and serve it warm with a pat of butter.

1. Preheat the oven to 425°F (220°C). Line a 10 × 15-inch baking pan, such as a Pyrex, with parchment paper.
2. In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
3. In a medium bowl, whisk together the melted coconut oil, sourdough discard, sour cream, and eggs until smooth.
4. Pour the wet ingredients into the dry ingredients and stir just until mostly combined. Do not overmix.
5. Gently fold in the blackberries until evenly distributed.
6. Spread the batter evenly in the prepared pan. Sprinkle with streusel, if using.
7. Bake on the middle rack for 20 minutes, then move the pan to the lower rack and bake for an additional 10 minutes. The bake is done when the top springs back lightly when pressed or a skewer inserted in the center comes out clean.
8. Cool in the pan for 20 minutes to set. Cut into squares and serve warm, ideally with a pat of butter.

• Yield: One 10 × 15-inch pan, approximately 12–16 generous squares.
• Storage: Cover and keep at room temperature for up to 2 days, or refrigerate for longer freshness.
• Frozen berries: You can use frozen blackberries straight from the freezer. Fold them in gently so they do not break apart too much.
• Streusel: A sprinkle of homemade streusel gives the top a lovely bakery-style crunch, but this bake is delicious without it too.