In a small bowl whisk together the flour, the salt, the baking soda, the baking powder, and the pepper. In a bowl cream together the shortening and the sugar, beat in the egg and the buttermilk, beating until the mixture is combined well, and stir in the zucchini and the basil. Add the flour mixture to the zucchini mixture, stir the batter until it is just combined, and divide it among 24 well-buttered gem tins (each 1/8 cup). Bake the muffins in the middle of a preheated 400°F. oven for 15 to 18 minutes, or until a tester comes out clean, turn the muffins out onto a rack, and let them cool. Halve the muffins horizontally, spread the cut sides with the butter, and sandwich the radish slices between the muffin halves.