The cuisine of the dwarves (and the Gnomes who live side by side with them) is considered to be one of the more exotic cuisines within Artograch (in a negative way, from the point of view of the various Elven races), just like Lizardman cuisine. An important factor to consider when discussing the unorthodox cuisine of the Dwarven people is to take into account the conditions Dwarves live in: Living in the mountains, in caves and underground tunnels surrounded by rocky mountains perpetually covered in snow, with rather uneven population densities (large swaths of uninhabited or sparserly inhabited land interrupted by densely inhabited quasi-urban settlements), with only a few green valleys that are suitable for growing cereals, fruits and vegetables - conventional cuisine would be impossible without trade, which is precisely why Dwarven cuisine developed along rather unique and unorthodox lines.
Traditionally, cereal products were considered luxury rather than staple food: the majority of dwarves live in either subterran caves, tunnels and mines, or in partially-subterran cities such as Zorod Naugi im Pkhaur and Zorod Koldo im Neuna - only a small fraction of Dwarves live in the fertile and green valleys, tending to the barley-farms, vegetable-farms, fruit orchards, stables and livestock grazing grounds. As such, traditionally, for those who didn't live in those valleys, these products were expensive, meaning that in regular dwarven society, only the rich could effort to eat cereal products regularly.
All of this changed when the Dwarven territories after the Etrandish annexation of Dwarven clans - even though the Dwarves imported grain (and various other food products) from Etrand even prior to their integration into the kingdom, with the integration of the dwarves, this became even easier and more convenient. Imported grain is still not considered staple food, but it is certainly more accessible than ever before.
Fruits and vegetables
Just as with cereal products, fruits and vegetables were traditionally rather expensive for those who weren't involved in its production - and as such, they were never too prominent in traditional Dwarven cuisine. After the integration of the dwarven clans into the Kingdom of Etrand, the importation of dried fruits and vegetables became far more commonplace.
Mushrooms play a very important room in Dwarven cuisine: they tolerate the dark, and in fact thrive in the dark, which makes farming them in subterran farms not only possible, but in fact profitable. Fortunately for the dwarves, the caves and tunnels they inhabit are home to various edible mushroom species, and over the millenia, the dwarves have become experts at farming them. They are a staple food, eaten in a variety of ways: boiled, fried, dried, either cooked as is, chopped into small pieces, or mashed and used as a filling for another dish.
The biggest source of animal protein for Dwarves come from fish that swim in the underground rivers and lakes - the subterranean waterways are extremely rich with biomass, with a food chain starting from radiotrophic fungi and chemobacteria to the various carnivorous fish, with the Dwarves trying their best to catch them all, save for the bottom-feeders. Other sources of fat and protein come from insects, spiders, rats, pigs and chicken (fed with mushrooms, insects and worms). For Dwarves who live overground in the green valleys, goat meat and goat milk are common, but for all other Dwarves, those two are expensive luxuries.
Commonly considered a menace to non-Dwarven explorers, giant spiders are actually farmed for their "meat" by the Dwarves.
As the majority of dwarves live in the subterran, there are no reliable sources of water close to home - the various lakes and rivers within the tunnels and cave systems are suspected of being contaminated with both natural and man-made pollutants, and constantly climbing up to the surface to gather snow to melt is no good alternative.
Henceforth, ever since the beginnings of time, the dwarves have boiled the water they gathered and used various other means to purify it. But if one goes to all that length... why not go one extra step by adding some sugar and yeast to make some alcoholic beverages? Dwarves are famous for their love for alcoholic beverages, and are in fact the inventors of beer and usquebaugh in Artograch.
It is important to note however, that much of dwarven beer is different from beer produced by other races. While humans, halflings, goblins and other races make beer out of cereals, dwarves primarily make them out of different source materials: roots, mushrooms (whose chitin body walls can be broken down into glucose, which in turn can be fermented into alcohol), turnicates (whose cellulose body walls that can be broken down into ethanol) and even insect corpses (whose exoskeletons are made out of chitin).
It is easy to make beer out of roots with conventional methods employed by more primitive peoples. The science-minded dwarves and gnomes have also managed to breed new types of yeast that are capable of breaking down chitin (the material from which both mushroom "fibers" and arthropod exoskeletons are made of) into sugars such as glucose prior to fermentation - making it possible to cook beer out of mushrooms and insect corpses. Root beer is universally loved by all races, except by the cereal-phobic Lizardmen and smug High Elves who refuse to drink alcoholic beverages not made out of fruits. Mushroom beers have an exotic taste - and this time, in the good way, being the kind of exotic that other races appreciate. "Bug beer" on the other hand is considered distasteful not just by other races, but to a certain extent even by the dwarves themselves.
Perhaps it is the thickness and distastefullness of "bug beer" that propelled dwarves to experiment with distillation, leading to the invention of usquebaugh. Eventually, this became the preferred alcoholic beverage.
It is also important to note, that Dwarves typically drink their alcoholic beverages hot, rather than cold, and almost always with the addition of mulling spices, if available.
Tea is imported from the rest of Etrand, but it is typically only drank by the rich. Milk is also rather expensive, hence it is not a staple beverage. The only somewhat-prominent non-alcoholic beverage drank by dwarves is pseudo-coffee, made from roasted roots, which are then grinded into a fine powder, and put into a fabric - boiled water is ran through it, taking on the colour, taste and smell of the roasted roots.