In a mixing bowl, beat together the cream cheese, sour cream, and mayonnaise until fluffy.
Set aside a few slices of pepperoni and give the rest a rough chop.
Stir the pepperoni in to the cheese mixture along with 1 c of the mozzarella cheese and 1/4 c of the parmesan cheese. Also stir in the diced veggies (optional).
Spread the cheesy mixture into a shallow baking dish (a tart or pie plate works perfectly.)
In a small dish, mix together the sauce ingredients. Spread this over the cheesy mixture.
Top with the remaining cheeses and arrange the reserved slices of pepperoni on top.
Bake for 20 minutes or until bubbly. Allow it to rest 5 minutes before serving.