I don't know exactly what would be most profitable, but I'd be expecting simple sauces on pasta, rice and so on, along with salads. Stuff you can cook in batches, keep warm and serve lots of it fast. Omelettes may not be complicated but they are difficult to cook in batches and keep without them degrading. They're a good chef demo but easy to see how they might not be profitable.
I've not seen trollies on Austrian Rail Jet. At seat deliveries were ordered on the WiFi or by paper slip handed to catering staff and brought by tray. They seem to have far more staff than DB so I wonder if that's also run as a public service rather than for profit.
Most profitable?
The lack of profitability of onboard catering, even with inflated prices, is the entire point of what I am saying. Travelling Chef was a very long way from profitable.
The name of the game is minimising losses or breaking even if you are very lucky - because, guess what, most people use trains to get from A to B, not as some mobile culinary experience. All these passengers you seem to think are going to buy lots of hot food fast do not exist. Whereas lots of people do exist who are travelling around these days with expensive electronic devices of all shapes and sizes that they are not keen to leave unattended while they go off in search of a buffet car.
The catering services that DB and OBB provide that send some posters here into raptures are not profitable. Try finding a restaurant or bistro car on a train in France, the home of fine dining. SNCF wasn't willing to shoulder the losses. There isn't even complimentary food in first class on most TGV services, except where it went down the road of an airline-type offer for the international Eurostar and TGV Lyria (services to Switzerland that take a while, as most of the route is not on an LGV high-speed line).
In part, their approach was influenced by the impact of reduced journey times thanks to TGVs - an effect that was seen in this country a long time ago, in the late 1970s when HSTs supplanted loco-hauled trains and the lavish over-provision of catering on early HSTs was rapidly reined back, due to low demand for restaurant car meals.
Even Amtrak, with interminably long journeys across the US, has been cutting back to basic pre-packed airline-type food on a number of services in recent months, due to heavy losses.
If I was a First Group Director and Shareholder I would be wanting to know why we are loosing our passengers' refreshments business formerly conducted on our trains to our commercial advantage, to the likes of Sainsburys and M&S at Paddington and at other Organization's station buffets.
For crying out loud, there is no commercial advantage to it - it would probably be more commercially advantageous to First Group, and other operators, just to forget about any type of on-train catering. Which is just what Chiltern Railways did to its morning peak offering not very long ago, even on London-Birmingham runs taking a couple of hours.