As far as I know, malting is an activity performed only by brewers, distillers, and manufacturers of malted milk. So what kind of beverage is the cat in this cartoon preparing?
What the cat is doing, of course, is meant to be moulting (BrE) / molting (AmE): tiresomely shedding hair all over the carpet, the furniture, and people’s laps.
This is an interesting spelling mistake, because it seems to imply that the cartoonist, Nick Edwards, pronounces malt and moult identically. If, like me, he pronounced malt mɔːlt, i.e. with the THOUGHT vowel, and moult məʊlt, with the GOAT vowel, he would be unlikely to confuse them in spelling. The same applies, if like many other British people, he pronounces malt as mɒlt, with the LOT vowel, just as long as it’s still distinct from moult. And the point still applies if, like many people, he has a noticeable pre-dark-l allophone for GOAT, so pronounces moult as something like mɒʊlt.
Sorting out the possible mergers of vowels in the context of a following preconsonantal or final l is tricky. Even in London, let alone the rest of the southeast of England, there seems to be considerable variability. A trainman on Wimbledon station regularly announces trains as calling next at ˈeosfɪod Earlsfield, implying the existence of possible homophones such as well–whirl and fill–feel. One of the coaches at my running club, who would never do anything so vulgar as to drop an h, nevertheless momentarily confuses some of us by having hill and heel as homophones hɪo.
This is by no means only a working-class phenomenon: I remember the eminent (and rather posh) phonetician Gillian Brown telling me she had several of these contextual mergers of the back vowels before l in her own speech.
There is one group of southeasterners who, unlike most, merge LOT and GOAT in this environment, so that doll and dole are homophonous. Furthermore, rather over half of the English have LOT rather than THOUGHT in the set fault-malt-halt-salt (see LPD charts for salt). If the cartoonist belongs to both these groups, there is our explanation of confusion over the spelling of moult.
The cartoonist is aware of the misspelling, and says he will change it eventually. Meanwhile, let me thank him for providing me with an apt example.