How sad to contemplate hanging out in a hotel lobby with the risk of being asked to leave.

1) Take the Malpensa Express to Milano Nord Cadorna station. The station is only a few minutes' walk (underground) from T1 arrivals (and you can even purchase tickets in the baggage hall if you wish).
2) Book tickets for the 11:00 viewing of Leonardo da Vinci's 'The Last Supper' – only a 10-12 minute walk from the station. There's availability at present, but it tends to sell out quickly. Here's the official site: http://www.vivaticket.it/index.php?nvpg[home]&op=cenacoloVinciano&change_language=1
3) Have a 'real' Italian lunch.
4) Take the Malpensa Express back to the airport in good time for your flight.

NB easyjet flies out of Terminal 2 – so in any case you'll have to make your way over there.
NB Milan can get ver cold and foggy in the winter – so bring a coat.