01 -
Set your oven to 375°F (190°C) and line your muffin tray with paper cups.
02 -
Stir together the plain flour, salt, baking powder, and sugar in a large bowl until they're evenly mixed.
03 -
In another mixing bowl, whisk the eggs, vanilla, milk, and melted butter. Add this into your dry mix, stirring just enough to combine.
04 -
Gently add in the sour cream and stir until the batter has a nice smooth texture.
05 -
Mix together the cinnamon and brown sugar in a little dish to make the swirl.
06 -
Pour batter halfway into each muffin liner, sprinkle on the cinnamon sugar mixture, and top it with more batter till cups are 3/4 full.
07 -
Bake them for about 18 to 20 minutes. To test, stick a toothpick into the center; it should come out without batter.
08 -
As muffins cool off a bit, blend the icing sugar and milk till smooth. Drizzle it over the muffins while they're still warm.