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Featured image Aerial shot of the top of oversized, jumbo chocolate muffin on wood board with remaining muffins surrounding it.
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Copycat Costco Double Chocolate Muffins

These Copycat Costco Double Chocolate Muffins are oversized bakery-style muffins that are ultra-moist, packed with deep chocolate flavor, and loaded with melty chocolate chips in every bite.
Course Breakfast
Cuisine American
Keyword double chocolate muffins
Prep Time 15 minutes
Cook Time 25 minutes
Total Time 40 minutes
Servings 6 jumbo muffins
Calories 793kcal
Author Tawnie Graham of Kroll's Korner

Ingredients

  • 1 3/4 cups all-purpose flour spooned and leveled
  • 2/3 cup unsweetened cocoa powder sifted if clumpy
  • 1 Tbsp. baking powder
  • 1 tsp. baking soda
  • 1 tsp. salt
  • 1 tsp. espresso powder optional
  • ½ cup butter, unsalted melted and slightly cooled
  • 1 ¼ cup granulated sugar
  • 2 large eggs room temperature
  • 2 tsp. vanilla extract
  • 3/4 cup buttermilk* room temperature
  • 1/2 cup sour cream room temperature
  • 2 cups semi-sweet chocolate chips divided
US Customary - Metric

Instructions

  • Preheat and prep: Preheat oven to 425°F and line a 6-count jumbo muffin pan with jumbo muffin liners. Set aside. (Note: you can make smaller muffins in a regular sized muffin tin. See recipe notes).
  • Whisk dry ingredients: In a medium-sized mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, salt, and espresso powder (if using). Set aside.
    1 3/4 cups all-purpose flour, 2/3 cup unsweetened cocoa powder, 1 Tbsp. baking powder, 1 tsp. baking soda, 1 tsp. salt, 1 tsp. espresso powder
    Dry ingredients for double chocolate muffins whisked together in clear mixing bowl with whisk.
  • Melted butter & sugar: Whisk the slightly cooled melted butter and sugar in a large mixing bowl.
    ½ cup butter, unsalted, 1 ¼ cup granulated sugar
    Side-by-side image adding the melted butter and sugar then to a bowl then mixing together before adding the rest of the wet ingredients.
  • Add wet ingredients: Add eggs in one at a time, followed by the vanilla extract. Then add the sour cream and buttermilk, whisk.
    2 large eggs, 2 tsp. vanilla extract, 1/2 cup sour cream, 3/4 cup buttermilk*
    Side-by-side image showing mixing the sour cream and eggs to the butter and sugar then combining the rest of wet ingredients and stirring to combine.
  • Add dry ingredients: Fold in the dry ingredients and 1 ½ cup chocolate chips. (Reserve the other ½ cup for topping on the muffins). Careful not to over mix. The batter will be very thick. Allow the batter to rest for 10-15 minutes at room temperature.
    2 cups semi-sweet chocolate chips
  • Scoop into muffin pan: Divide the batter into the prepared jumbo muffin pan then top muffins with reserved chocolate chips. You should get 6 jumbo muffins, but if you feel like the batter is getting too close to the tops, make a couple small/regular sized muffins to avoid spilling over the edges.
    Side-by-side image of batter mixed for chocolate muffins then poured into jumbo muffin tins lined with parchment paper liners.
  • Bake: Bake for 5 min at 425°F, then reduce oven temperature to 350°F (without opening the oven) and bake again for ~19-25 minutes. Try not to open the oven door too much or too early, as this can cause temperature fluctuations and the centers may sink. (Also, ovens vary. You'll know the muffins are done when they have risen and a toothpick inserted in the center has a few moist crumbs attached, but nothing wet or goopy). Careful not to overbake these beauties!
  • Cool and enjoy: Cool in the muffin pan for a few minutes, then enjoy!
    Upclose shot of chocolate muffin on plate with bite taken out.

Video

Notes

Storage:
  • Room Temperature: 2–3 days in an airtight container.
  • Refrigerated: Up to 1 week in an airtight container.
  • Frozen: 2–3 months wrapped tightly in plastic wrap and stored in a freezer-safe bag or container.
* Regular sized muffins: follow the same directions and bake at 425°F for 5 min, then 350°F for ~10-12 minutes. Ovens vary.  
*Buttermilk: If you don't have buttermilk, you can make it by adding 1 Tbsp. white vinegar or fresh lemon juice to 1 cup whole milk and allowing to rest for 5 minutes. OR you can just use whole milk in its place entirely. Since the recipe also has sour cream, it will still turn out moist and yummy. 
* Sour cream: Full fat plain Greek yogurt may be used in place of sour cream. 

Nutrition

Serving: 1jumbo muffin | Calories: 793kcal | Carbohydrates: 116g | Protein: 14g | Fat: 33g | Saturated Fat: 18g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 10g | Trans Fat: 0.1g | Cholesterol: 80mg | Sodium: 727mg | Potassium: 690mg | Fiber: 10g | Sugar: 67g | Vitamin A: 354IU | Vitamin C: 0.3mg | Calcium: 287mg | Iron: 8mg