[Charli]

HD sells expanding foam that has a bitter taste. Supposed to keep mice out. Bought some for our sticks and brick basement but haven't tried it. Steel wool might work although pest control places sell a similar product but it is coarser and sharper so mice won't eat through it. I'd stuff the hole with steel wool or like product and then stick the spray foam nozzle into the steel wool and fill the gap with foam. You get protection from the mice with the bonus of added insulation.