Preheat oven to 400°. Butter 3 large baking sheets and set aside.
In a medium pan over medium heat, melt 1/2 cup butter with 1 cup water; bring mixture to a simmer. Reduce heat to low and immediately add flour, sugar, and salt all at once. Stir vigorously with a wooden spoon until the mixture forms a ball that pulls away from sides of pan, about 1 minute. Remove from heat.
Add eggs one at a time, stirring vigorously to fully incorporate each egg before adding the next. The mixture will appear to separate at first; keep stirring until dough comes together into a smooth paste.
Divide dough evenly among the 3 prepared baking sheets. Using a spatula, spread dough into 8-in. circles.
Bake pastry layers 20 minutes, then reduce heat to 350° and bake until browned, 10 to 15 minutes. (Pastry may be baked in batches.) Transfer layers to cooling racks and set aside. Meanwhile, spread coconut on a baking sheet and bake at 350° until lightly toasted, about 10 minutes.
In a large bowl, beat cream to soft peaks. Add powdered sugar and beat to combine.
Spread each pastry layer with 1 tbsp. preserves, then top each with 1/3 of the whipped cream and 1/3 of the coconut. Stack the circles and slice with a serrated knife.
Note: Nutritional analysis is per serving.