Preheat oven to 350.

In a large mixing bowl, add butter and beat on medium for 30 seconds. Add garlic, sugar, baking powder, Italian seasoning and 1 ounce (about 1/4 cup) Parmesan cheese. Mix until completely combined. Beat in egg and milk. Mix in as much flour as you can with the mixer, then use a wooden spoon to stir in remaining flour, pepperoni, red sweet pepper, onion, and parsley - it should be fairly dry.

Scoop the dough out onto a lightly floured surface and knead the dough a few times until it holds together. Divide the dough in half and shape each into a 9" x 1 1/2" roll. Scatter the counter with the remaining Parmesan cheese and roll each dough back and forth to coat them with the cheese. Place the dough on to a parchment lined baking sheet and flatten slightly.

Bake until the top feels firm to the touch, about 20 to 25 minutes. Remove and let cool on the baking sheet for about 35-45 minutes.

If you turned the oven off, reheat it to 325 degrees. Cut each roll diagonally into generous 1/2" slices. Place the slices back onto the cookie sheet and bake for 10 minutes - turn the biscotti over and continue to bake until they have started to crisp up, about another 10 to 12 minutes. Remove and place the biscotti on a wire rack to cool.