Should we use plasterboard, MDF or wood when blocking up a window in our pantry?
In most localities it is illegal to permanently block a window from the inside only. The reason being in an emergency fire fighters may waste time trying to enter a blocked window. The amount of difficulty to do it properly will vary based mostly on the type of exterior siding. I would remove the window, frame it in with 2x4's or what ever the wall is framed with. Install any blocking that will help with mounting the shelves. Install sheathing to allow the siding to fit flush with the exterior. Install plasterboard to fit flush with the existing interior wall including any insulation.