1. In a small frying pan, melt butter and add shallots, cook on medium low heat until, soft and tender. Remove from pan, cool and set aside until needed.
2. Preheat oven to 425 degrees F.
3. In a large bowl stir together flour, baking powder, baking soda, sugar and salt.
4. Cut in the shortening until it resembles fine bread crumbs, then stir in the cheese, cooled shallots and the mashed potatoes.
5. Beat the egg and buttermilk together and pour into the flour, cheese and potato mixture all at once, stirring lightly until you have a soft sticky dough.
6. Add the dough to a lightly floured surface and pat into a large circle about 3/4 to an inch thick. I use a water glass to cut out the dough.
7. Place the scones on an ungreased cookie sheet and bake in a 425 degree oven for 10 - 12 minutes, until golden brown.