Grandma's Famous Bologna Salad

Ingredients

• 1 1/2 pounds bologna, cut into chunks
• 1 egg, hard-boiled, plus more, to taste, sliced, for serving
• 1 stalk celery, roughly chopped
• 2 teaspoons onion, finely chopped
• 2 teaspoons sweet pickle relish
• 3/4 cup mayonnaise
• 1 tablespoon yellow mustard
• salt, to taste
• black pepper, to taste
• white bread slices, to taste, for serving