1Cream together 1 c softened unsalted butter and 1/2 c brown sugar until smooth.
2Add 1 egg and mix until combined.
3Add 3/4 c powdered sugar, 2 tsp vanilla extract, and a pinch of salt. Mix until combined.
4Gradually add 2 1/2 c flour and mix until just combined.
5Line an 8x8 pan with parchment paper and spray with non-stick. Divide dough in half and press one half into the pan. Take out for a moment to shape the other half, set aside and replace with the other half.
6In a small bowl, mix 1 c brown sugar, 1 tbsp cinnamon, and 2 tbsp flour. Then incorporate 3 tbsp melted butter.
7Spread the mixture evenly over the first layer of dough in the pan. Then, add the top layer of dough and slightly push down.
8Bake at 325 F for 30-40 min until the top is set.
9Whisk together 1 c powdered sugar, 1 1/2 tsp cinnamon, 1/2 tsp vanilla, a pinch of salt, and 4 tbsp heavy cream.
10After completely cooled, apply the frosting and let it set up.