Add the flour, baking powder, and baking soda, and mix until almost combined. Let the batter sit at room temperature for at least 30 minutes. This step creates the signature domed tops that the best muffins have!
Make the streusel topping
Into a medium mixing bowl, add the flour, brown sugar, kosher salt, and cinnamon, and mix with a whisk.
Add the melted butter and mix until the streusel topping comes together.
Pour the batter into the muffin tins filling almost to the top using an ice cream scooper or a large cookie scooper.
Top the muffins with about 1 ½ tablespoons of the streusel topping and press the streusel topping onto the muffin batter so it sticks and does not fall off while baking.
Bake in a 200c (400f) preheated oven for 5 minutes, and then bake for another 10-12 minutes at 180c (350f) or until a toothpick comes out clean.
Allow the muffins to cool for at least 20 minutes before serving. Top the muffins with a simple two Ingredient glaze and serve!
Notes
Don't skimp on the streusel. Be generous when sprinkling the streusel topping on each muffin. Press it gently into the batter to ensure it sticks during baking.
Use an ice cream scoop or large spoon to fill each muffin cup about ⅔ full. This allows room for the muffins to rise without overflowing.
Use room temperature ingredients. It is important that you use room-temperature ingredients like eggs and milk. This step ensures that your mixture mixes into a homogenous mixture and bakes perfectly.
Don’t overmix the batter, you don’t want to develop the gluten in the flour. This step ensures you have moist muffins and not dense and dry muffins.
Measure you flour correctly! When measuring your flour, avoid scooping it with a measuring cup. Instead, stir the flour with a spoon to create as many air pockets as possible, and spoon it into your measuring cup. Finally, level it with a back of a knife.
Avoid overbaking! Check your muffins a few minutes before the recommended baking time. They're done when a toothpick inserted in the center comes out clean or with just a few moist crumbs.
Be patient! I know it's extremely tempting to eat these muffins as they are pulled out of the oven, but let these muffins cool for at least 15 minutes so they will be more firm and won't crumble up.