Line a small cookie sheet or similar pan with parchment paper. Pulse mixed nuts in a food processor 5 - 6 times, or more if you want a finer blend. Spoon processed nuts into a bowl. Set aside.
Into a large bowl combine ham, cream cheese, shredded cheese, diced onion and spicy brown mustard. Mix well into all ingredients are well incorporated.
Using a ¼ measuring cup, scoop cream cheese mixture into the palm of your hands. Wearing latex gloves is a must, roll mixture into a ball. Repeat until finished. This should make 7 - 8 balls.
Place each one on the parchment paper lined cookie sheet.
One by one place a cheese ball into processed nut mixture using a spoon or your fingers press coating into cheese ball mixture. Coat evenly. When finished place Mini Ham Cheese Balls into the refrigerator to chill.