Preheat oven to 350F.
In a medium saut pan over medium to high heat, add pepperoni and cook until crispy. Remove and drain on paper towels. When cool, crumble pepperoni and set aside 3/4 for tossing in stuffing, reserving 1/4 for garnish.
To the remaining grease in the pan, add yellow onions, peppers, celery, garlic and sun-dried tomatoes, and saut until onions are translucent. Remove and let cool.
In a small bowl, whisk together the eggs, pepper and paprika. Place foccacia cubes, parsley and green onions in a large mixing bowl and pour egg mixture over everything. Add sauted vegetables and crumbled pepperoni, and mix all ingredients thoroughly. Slowly add chicken stock, tossing everything so it's absorbed evenly.
Lightly butter a 13 x 9" pan and add the stuffing. Cover with aluminum foil and bake for 35 minutes, then remove foil and bake for another 15 minutes to brown the top.
When finished baking, garnish with parmesan cheese and reserved pepperoni crumbles.