Welcome to the forum, You.
How about giving us a first name to call you?
I don't think thinset will bond to polyurethane, but there are ways to get around that. The first thing the pros will want to know is if your counter top is strong/stiff enough for tile. Tell us more about its construction.
Once we're certain its strong enough, you could probably attach a 1/4" layer of CBU, properly thinset and screwed. Or, you could attach a 1/2" of plywood and put Ditra over that. There are likely even better ways that the ones I just mentioned.