Step 1: Prepare Crust - Freeze the unsalted butter. Combine flour, salt, and sugar. Add shortening and frozen butter, pulse until crumbs form. Gradually add ice-cold water; shape into a disk and chill for 30 minutes.

Step 2: Bake Crust - Preheat oven to 375°F (190°C). Roll out the dough, transfer to pie plate, trim edges, chill for another 15 minutes. Line with parchment paper, fill with weights, bake for 20 minutes, remove weights, bake for another 15 minutes until golden. Cool on wire rack.

Step 3: Make Filling - Bloom gelatin in cold water. Stir together sugar, flour, and salt with milk in saucepan over medium heat, bring to gentle boil. Remove from heat, add gelatin, cool to room temperature.

Step 4: Fold in Ingredients - Whip cream to stiff peaks. Beat egg whites with cream of tartar to stiff peaks. Fold whipped cream, egg whites, and coconut into cooled milk mixture.

Step 5: Assemble Pie - Pour filling into cooled crust, smooth top, cover with plastic wrap and refrigerate for at least 4 hours or overnight.

Step 6: Prepare Toppings - Whip additional cream to stiff peaks. For strawberry sauce, mix strawberries with confectioners' sugar, let sit for 10 minutes.

Step 7: Serve - Slice pie and plate each slice with strawberry sauce.