I find that I'm usually hungry after arrival, despite the small meal served on the plane before landing. In the same situation, I'd probably collect luggage and then head for the Malpensa Express. You can buy your tickets at the station, either from a Kiosk or staffed ticket office. Note that there are two destinations for the M.E. One train goes to Milano Centrale and the other to Milano Nord Cadorna so be sure you board the correct train. The trip to Centrale will be about 52 minutes. DON'T forget to validate your tickets prior to boarding the train or you'll face hefty fines which will be collected on the spot!
When you arrive at Milano Centrale, there are LOTS of food outlets - https://www.milanocentrale.it/en/store/index/food . If you want a sit-down restaurant rather than fast food, have a look at Roadhouse Grill.
If you'd rather carry on straight to Varenna, the total trip will be 2H:10M. There are departures from the airport at 12:13 and 13:13, and many others. It's not likely you'll be able to connect with the 12:13 departure so 13:13 is more likely. The 13:13 departure has a 15 minute layover at Milano Centrale, so you could buy a Panino or whatever to eat on the train. Be sure you determine the Binario or your train to Varenna before looking for food. You'll likely have a separate ticket for the train to Varenna, and DON'T forget to validate that also before boarding the train.
The trip to Varenna is 1H:03M, and I'd suggest sitting on the left when facing the front of the train. The train arrives at 15:23. The train goes through a tunnel just prior to arrival, and you'll need to be ready to disembark promptly as the train doesn't stop for long. The walk to Albergo Milano is not difficult, although you'll probably be running out of steam at about that time. You can have a "power nap" after checking in, and then decide whether you want to have a fine meal that evening or save that for another night.
