Preheat your oven to 350F
In a large bowl combine your butter, brown sugar and powder sugar. Mix until butter and sugar are creamed together.
Add in your egg and vanilla and mix again.
Add in your flour and cinnamon and mix until a dough forms.
Split your dough in half and add ½ to a lined 8x8 baking dish. Press dough until it is flat.
Take the other ½ of the dough and press it into an 8x8 square on a piece of parchment paper.
Make your brown sugar cinnamon filling by mixing all ingredients (½ cup brown sugar, 2 tbsp melted butter, 2 tbsp all purpose flour, 1 tbsp cinnamon) in a small bowl.
Add to your 8x8 baking dish then top with the other half of your dough.
Bake in the oven on 350F for 40 minutes.
Allow your poptart to cool for 15 minutes before icing them.
While poptart cools, make icing by mixing ingredients (1 cup powder sugar, 1 tsp vanilla, 1 tsp cinnamon, 2 tbsp milk) in a small bowl.
After poptart has cooled for 15 minutes, ice, slice, and eat!
