Grease a 8x11 or similar sized baking dish with butter or non-stick cooking spray.
Add diced bread to a large, rimmed baking sheet. Bake in the oven for 15-20 minutes or until toasted and stale. Cool completely. Increase oven temperature to 375 degrees. Transfer the bread cubes to a large mixing bowl.
While the bread toasts, heat a large skillet to a medium heat. Add 4 tablespoons butter. Once butter has melted, add onion, celery, leeks, sage and 1/2 teaspoon salt. Saute until leeks and onions are soft, about 6-7 minutes. Add poultry seasoning and chopped parsley. Cook another minute. Remove from heat.
Add chicken stock, remaining butter and Bouillon to a large liquid measuring cup. Microwave in 30 seconds increments until the butter has melted. Add eggs and whisk to combine. Pour the warm veggies over the bread. Use a wooden spoon to combine the bread with the veggies. Pour the chicken broth and egg mixture over the bread along with the remaining 1/2 teaspoons salt on top. Toss until combined.
At this point if you like a more wet stuffing, add a little bit more chicken stock. Season to taste with salt and pepper.
Transfer stuffing to prepared baking dish. Cover with foil and bake for 30 minutes. Remove foil and bake another 10-15 minutes or until golden brown and slightly crisp.