Preheat oven to 400°. Rinse and drain blueberries. Mix flour, sugar, baking powder, and salt in a medium bowl. Add shortening, egg, and milk and stir well, making sure that the shortening is fully incorporated. Add blueberries, and fold in gently. Use butter to grease 9 cups in a standard size muffin pan. Fill the greased muffin cups until they are a little more than 2/3 full. Bake in a 400° oven for 15 to 20 minutes or until golden brown and a toothpick inserted comes out clean. Serve hot with butter.