Butter 1 loaf of bread. Spread half the slices with strawberry jam, then top each slice with remaining slices to make sandwiches.
Butter the remaining loaf of bread.
Spread half the slices with Nutella, then top with remaining slices.
Remove the crusts from all the sandwiches, then cut each into 4 triangles. Lay the sandwiches on two separate platters long-edge down to form 2 long pyramids.
Spread the remaining butter along one side of each pyramid. Sprinkle the buttered-side of the jam sandwiches with the 100s and 1000s and the chocolate sandwiches with the chocolate sprinkles.