Preheat the oven to 350 degrees F.
Butter and flour four 7-inch round cake pans and line bottoms with parchment.
Cream together the butter and sugar. Add in the eggs, 1 at a time, mixing well after each.
Whisk together the flour, baking powder and salt. Stir the coconut flavoring and vanilla into the buttermilk.
Add in 1/3 of the dry mixture into the creamed butter/sugar mixture. Mix. Add in 1/2 of the buttermilk. Mix again. Repeat till all the flour and buttermilk are combined. Fold in 1/2 cup shredded coconut.
Divide batter evenly among the cake pans. Bake in preheated oven for 40 to 50 minutes till a toothpick inserted comes out clean.
Spread the remaining 1/2 cup coconut evenly on a baking sheet. Bake in a preheated 350 degree oven for about 10 minutes till nicely browned, stirring every couple of minutes. Let cool.
For the buttercream: Cream together the butter and shortening. Gradually add in the powdered sugar. Add in the milk, vanilla and desired amount of food coloring. Mix till combined.
To Assemble: Roughly chop 1 box of Samoa cookies. Starting with the first layer of cake, spread about 1/4 cup of frosting across the top. Sprinkle 1/3 of the chopped cookies in the middle of the layer, leaving a 1/2 inch border around the edge. Drizzle some of the dulce de leche over the cookies. Top with the next layer of cake and repeat this process 2 more times, then top with the last layer of cake. Cover the whole cake with the purple frosting. Place whole Samoa cookies onto the cake in a pattern and add toasted coconut along the top edge of the cake.