Blueberry Muffins
"The size of a softball. The top is the best part. You know it, we know it, the streusel knows it."
Costco Copycat — This is a homemade version of the Costco Bakery item. See it in store →
The Game Plan
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Preheat oven to 375°F (190°C). Line a muffin tin with paper liners or grease generously. For truly Costco-sized muffins, use a jumbo muffin tin if you have one.
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Make the streusel first: combine flour, sugar, and cold butter cubes. Pinch with your fingers until you get coarse, crumbly chunks. Refrigerate while you make the batter.
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Whisk flour, sugar, baking powder, and salt together in a large bowl.
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In a separate bowl, whisk melted butter, eggs, sour cream, milk, and vanilla until smooth.
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Pour the wet ingredients into the dry and fold gently — stop when you still see a few flour streaks. Overmixing is the enemy of a tender muffin. Walk away if you have to.
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Toss the blueberries with 1 tablespoon of flour (this prevents sinking), then gently fold them into the batter.
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Fill muffin cups ALL the way to the top. Pile it up. Be bold. This is not the time for moderation.
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Sprinkle streusel generously over each muffin, pressing lightly so it sticks.
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Bake 24-28 minutes until the tops are golden and a toothpick comes out clean. The kitchen will smell unreasonably good.
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Cool in the pan for 5 minutes, then transfer to a wire rack. Try to wait at least 10 more minutes before eating. Try.
