• Preheat the oven to 425°F. Add paper liners to a 12-cup muffin pan. Measure out the blueberries. Put them in a bowl or bag and put that container back into the freezer until ready to use the blueberries. Do not let the blueberries thaw.

Make the Muffin Batter

• Melt the butter over medium low heat and cool until it is barely warm, about 90°F. Crack the eggs into a small bowl.
• Place 2 cups (250 grams) of flour, the baking soda, and salt in a bowl and whisk for 30 seconds to combine.
• Place the sugar, cinnamon, and cardamom in a large bowl. Add the eggs and vanilla extract. Whisk for 1 minute until the mixture is creamy and lighter in color.
• Place the bananas in a medium sized bowl and use a fork or potato smasher to mash them up. Then use a whisk to make them creamy. Add the bananas to the batter and mix until fully incorporated.
• Add the cooled melted butter and whisk until thoroughly mixed. Next whisk in the sour cream and let the batter sit for 5 minutes.
• Toss 1-1/2 cups (225 grams) of the blueberries with 2 teaspoons of flour.
• Add 1/2 of the dry ingredients to the batter and fold it with a silicone spatula until incorporated. Add the remaining dry ingredients and mix in until there are no white streaks of flour. Scrape the bottom of the bowl to ensure all the ingredients are thoroughly combined. Add the blueberries and fold them into the batter.

Bake the Muffins

• Divide the batter even between the 12 muffin cups. Take the remaining blueberries and top each muffin with 3-4 blueberries. Bake the muffins at 425°F for 7 minutes and then without opening the oven door reduce the temperature to 350°F. Bake the muffins for another 14-16 minutes until the internal temperature registers at about 200°F using an instant-read thermometers.
• Cool the muffins in the pan for 5 minutes, them move the muffins to a wire cooling rack.

Store the Muffins

• The muffins can be stored at room temperature in an airtight container for up to 3 days. To freeze the muffins wrap each muffin in plastic wrap. Store the muffins in a freezer-safe bag or container. Label and date the bag and freeze for up to 2 months.
• To reheat the muffins, thaw them overnight in the refrigerator or at room temperature for about an hour. Warm the muffins in the microwave or in the oven for 5 minutes at 350°F.