Underlying white for aluminum foil printing

Hello I'll be a total amateur, which I am. At work they wanted me to try to make graphics for chocolate characters for Bethlehem. As for the design, I have it done, but I don't seem to really understand how it is with the background white. For example, here with the cow, I made the underlying white so that in reality the cow and straw were shiny. The rest should be matte, but I got a response from the management that it was wrong. Especially with a cow, where it would completely change colors. Both white and brown spots. They want me to make the background shine and the cow not. Does this mean that I should just swap the underlying white with a transparent background? Or is there someone who would like to explain to me the basic undelying white in the case of aluminum foil? Thank you very much.

(Blue is representing the underlying white)