Melt 6 tablespoons of the butter in a 5-quart pot together with the bay leaves over high heat. When butter is melted, add the onions. Cook, stirring frequently, until onions are beginning to brown on the edges, about 5 minutes. Add the celery, bell peppers, garlic, and Seafood Magic. Cook, stirring frequently, until the celery and bell peppers are faded in color, about 4 minutes. Add the shrimp and stir in well. Add the remaining 2 tablespoons of butter and stir until butter is melted. Add half of the breadcrumbs. Cook, stirring constantly, until the breadcrumbs are fully moistened and blended in, about 2 minutes. Add the remaining breadcrumbs and continue to stir until all the breadcrumbs are mixed in, about 2 minutes. Remove from heat, pull out bay leaves and stir in the Poultry Stock. The dressing should be bound and thick but not wet.
Spread the dressing on a sheet pan as thinly as possible. Refrigerate sheet pan in the coldest part of the refrigerator until dressing is very cold. (Note: The goal is to chill the dressing as quickly as possible. Spreading the dressing in a thin layer on a sheet pan allows it to cool very quickly. In our refrigerator, this took a little over 1 hour.)