plastering over stone tiles?

hi

i put natural stone (travetine) tiles behind my range cooker a few months back and they are clashing with a canope feature made out off old stone...

i basically want a smooth plaster finish now covered in clear glass(to protect from grease etc)....

can these tiles be plaster over? i dont fancy the mess of trying to take them down and smoothing over the bumpy wall left behind?

what the best thing i should do..thanks!!!