For the muffins: You'll need flour, baking powder, baking soda, cardamom, salt, butter, sugars, milk, yogurt, vanilla, eggs, and pistachios.
For the streusel: You'll need pistachios, butter, brown sugar, cardamom, and oats.
Make the streusel
Combine the oats, brown sugar, and cardamom. Cut the butter into the mixture until fully combined, then stir in the chopped pistachios.
Make the batter
Cream together the butter and sugars, then add in the eggs and vanilla. Alternate adding the dry and wet ingredients, then fold in the finely ground pistachios.
Fill the muffin liners (spaced apart for even heating) and top with streusel. Bake at 425 degrees F for 5 minutes then at 350 degrees F for another 14 minutes.
Cool on wire rack
Transfer the muffins to a wire rack to cool completely.
Dust with powdered sugar
Once cool, dust each muffin with powdered sugar.
Serve for brunch or an afternoon snack!