Preheat oven to 375 degrees
In a large bowl mix together the flour, baking soda, and salt
In a stand mixer cream together butter and sugar for at least 2 minutes.
Add eggs and yogurt to butter mixture and cream for another 2 minutes.
Add vanilla and let mix for another 30 seconds.
Slowly add in flour mixture, and let incorporate fully.
Spray a 18 x 13 jelly roll pan with non-stick cooking spray or line with parchment
Carefully press the dough into the pan so it is nice and even (you can use a rolling pin)
Bake 18-20 minutes until just barely golden brown on edges.
Let cool completely.
Mix together frosting ingredients in a large bowl using a hand mixer or stand mixer, whipping until fluffy.
Use a spatula to spread the frosting over the bar
Cut into squares and enjoy!