Preheat an oven to 350 degrees F (175 degrees C). Grease and flour a 9x9-inch square baking pan.
Whisk 2 cups flour, baking powder, and salt together in a mixing bowl; set aside. Toss the blueberries in a little of the flour mixture until coated; set aside.
Beat the shortening and 1 cup sugar with an electric mixer in a large bowl until light and fluffy. Beat in the egg. Pour in the flour mixture alternately with the milk, mixing until just incorporated. Fold in the floured blueberries, mixing just enough to evenly combine. Pour the batter into prepared pan.
To make the topping, combine 3/4 cup sugar, 3/4 cup flour, and the cinnamon in a bowl. Cut in the cold butter with a pastry blender until no small pieces of butter remain. Stir in the toasted coconut, then sprinkle the topping evenly over the cake.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 1 hour and 10 minutes. Cool in the pans for 10 minutes before removing to cool completely on a wire rack.
Frost is a common problem with wild blueberries and is the primary cause of a poor harvest. Not all blueberry farms have the same climate. The fields in Quebec and Maine blossom before the fields on Prince Edward Island and are therefore more susceptible to frost. The later blossoming of Island berries usually occurs after the last frost of the spring.