Heat oven to 300°.
Cut leeks in half lengthwise and wash leeks well to remove grit and sand. Thinly slice.
Using a large skillet or Dutch oven, combine Â¼ cup oil and ghee. Heat over medium heat until ghee is melted. Gently sautÃ© leeks and season generously with salt and pepper. Cover and cook, stirring occasionally and reducing heat to low until leeks are "melted" (very tender and lightly golden), about 40 minutes.
While leeks caramelize, spread bread cubes in single layers on baking sheets. Bake cubes, rotating pans once halfway through, until dried and lightly golden, 25 to 30 minutes. Let cool.
Optional: If using giblets, chop neck into 3 to 4 pieces. Heat 2 tablespoons of the remaining ghee in a small skillet over medium heat. Add neck pieces, heart and gizzard; season with salt and pepper. Cook, turning pieces occasionally, until giblets begin to brown, about 10 minutes, then transfer to a cutting board. Add remaining tablespoon ghee and liver to skillet; season with salt and pepper and cook over medium-high heat for 2 minutes; turn and cook 30 seconds more. Transfer liver to cutting board. Pick meat from neck, discarding the bones. Finely chop liver, heart and gizzards.
Increase oven temperature to 350Â°.
Combine (giblets), leeks and toasted bread in a bowl. Add remaining 1/4 cup oil. Season with salt and pepper and stir together well, then add chicken broth and stir to combine. Transfer to a large baking dish big enough to hold the stuffing in about a 2-inch layer.Bake until hot and deep golden brown, about 30-40 minutes.