Melt butter in a large skillet over medium-low heat. Add onion and garlic; cook, stirring occasionally, until golden brown, about 20 minutes.
Place bacon in another large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain bacon slices on paper towels, reserving grease in the skillet.
Cook pear slices in reserved bacon grease over medium-low heat until golden, 2 to 3 minutes per side. Drain pear slices on paper towels.
Beat eggs and egg yolks in a large bowl until smooth. Add heavy cream, black pepper, salt, and Italian seasoning; mix until well-blended.
Place half the bread cubes in a 9x13-inch glass baking pan. Sprinkle half the Gorgonzola cheese on top. Pour onion mixture over cheese. Spread half the bacon and pears on top. Repeat layering remaining bread, Gorgonzola cheese, and pears, ending with bacon. Pour egg mixture slowly and evenly over layers. Press down with a spatula or a gloved hand to prevent bread from overflowing.
Place baking pan in the refrigerator until bread soaks up egg mixture, at least 1 hour and up to overnight.
Preheat oven to 375 degrees F (190 degrees C).
Bake bread pudding in the preheated oven until top is golden brown, covering with aluminum foil if needed, 40 to 55 minutes. Remove from oven and let dish set before serving, about 15 minutes.
