Preheat oven to 350°F and grease mini muffin pan
In a small bowl weigh out flour and mix in salt, set aside
Melt butter either in a saucepan or in the microwave.
Add sugar to melted butter and mix completely
Add eggs and whisk thoroughly, then add in vanilla and whisk
Sift cocoa powder into butter mixture, then add espresso and whisk to mix in
Add in flour and mix in gently with spatula until just incorporated. Do not overmix
Spoon batter into muffin tray, filling each cup about 3/4 full.
I find my mini muffin tin tends to get stuck on my oven grates so I put it inside another cookie sheet. Bake on middle rack for 15 minutes.
Let brownie bites cool in muffin tin for about 60-90 minutes before removing from tray.
While brownies are cooling, place softened butter in a bowl with brown sugar, salt and vanilla and cream together.
Add powdered sugar in ½ cup at a time
Once brownies are cool pipe frosting (or use a knife) onto brownie bites. Enjoy!