A method of making an interior trim panel for attachment to structure of a vehicle includes the steps of placing a trim insert into a cavity of an apparatus and over a first seal thereof. The method also includes the steps of loading a retainer over the trim insert to sandwich the trim insert between the retainer and the first seal and closing the apparatus. The method further includes the steps of filling the cavity with a plastic material and introducing steam into the apparatus to expand the plastic material to form a substrate and bonding the substrate against the trim insert to form an interior trim panel.