Preheat oven to 425 degrees. Grease large baking tray.
Peel potato and cut into quarters. Place in pot and cover with water. Bring water to a boil, cooking for 10-12 minutes or until potatoes are done and a knife slides in easily. Drain potatoes and place in a large bowl. Mash potatoes roughly together. Blend well together milk, butter, cream, seasoning and cheese. Set aside.
Lightly flour a clean surface and roll out each pie crust into a long oval or rectangle. Cut each one into quarters. Place two slices of ham on half of the quarters, topped by mashed potato mixture. Place the other quarter of pie crust over it and crimp each corner with a fork to seal together. Whisk egg and lightly brush the surface of each pie. With a sharp knife, quickly slash three 1” long slits into the top. Gently place onto the greased baking pan and place in oven. Cook until golden brown or 10-12 minutes.
While the hand pies are cooking, make the hot mustard sauce by blending yellow mustard, hot sauce, honey, salt, and white wine vinegar into a small dish.
Once pies are ready, remove from oven and let them cool slightly. Serve with mustard.