In a medium saucepan, over medium high heat, bring 2 1/2 cups water to boiling. Remove from heat and whisk in cheese sauce mix and potato flakes. Allow mixture to sit 2 minutes, then whisk again until smooth.
Prepare frozen vegetables according to package directions, until crisp-tender (do not overcook). Stir drained vegetables into potato mixture; mix in pepper.
Place one slice of ham into 8 muffin cups or custard cups; press down slightly to mold the ham into a "cup" shape. Spoon potato mixture into the ham cups, dividing evenly.
Bake for 15 - 20 minutes or until lightly browned. Loosen ham around the edges with a small spatula before lifting them out of the cups. *If using leftover mashed potatoes, stir cheese sauce mix into 1/2 cup hot water. Whisk the cheese mixture into the mashed potatoes, then stir in vegetables and pepper. Proceed with Step 4 above.