Pi Day Pie

This pie was to celebrate Pi (3.14) Day in March 14. I was using a pizza dough instead of a pie crust for the bottom, and I use dutch style for the topping.

Ingredients:
For the crust/dough:
You can use a store-bought, ready-to-use pizza dough, but if you want to make it yourself, then here they are:
1 cup unbleached all-purpose flour
1 teaspoon yeast
1 teaspoon brown sugar
1/2 cup warm water (about 110-120°F)
3 tablespoon oil
a pinch of salt

For the filling:
2 granny smith apples, peeled and diced
2 tablespoon brown sugar
1 tablespoon butter
1 teaspoon cinnamon powder

For the topping:
1/2 cup unbleached all-purpose flour
1 tablespoon butter
2 tablespoon brown sugar
1 tablespoon cinnamon powder

For the frosting:
1/2 cup milk
3 tablespoon white sugar
1 tablespoon corn starch

Steps:

1. Make the dough. Put yeast and sugar to the water, stir, and wait for 5 minutes. Sift flour to a large bowl, make a hole in the center and pour the yeast solution onto it. Mix until the water spread evenly throughout the flour. Add oil and knead the dough until it gets soft, unstick, skin like texture. Cover the bowl, place in a warm place for an hour.
2. Make the fillings. Combine all of the fillings ingredients to a pan, cook with medium-heat until the apple soft enough but not mushy. 
3. After the dough left for an hour, it should doubled in size. Flatten it then sprinkle the salt, and re-knead until the salt dissolved evenly to the dough. Flatten the dough using a roller, as thin as you can get without damaging it. Put in the pie tin. You should have enough dough to make the pi symbol also. Wait for 10 minutes.
4. Make the toppings. Combine all of the topping ingredients coldly until they got sand like.
5. Pour the fillings, then the topping, then the pi symbol to the crusted tin. Bake with 350° until the toppings get browned.
6. Make the frosting. Combine all the topping ingredients to a small pan heat until it get gravy but still white in color.
7. Pour the frosting to the pie 1 minute before removing it from the oven.
8. Viola, you've made it.