In a way that is full of flavor; with strong, pleasant, or distinctive taste.
From 'flavourful' (British spelling) plus the adverb suffix '-ly' (from Old English '-lice'), which converts adjectives to adverbs describing how an action occurs or a quality is expressed.
Adding '-ly' to adjectives is how English makes adverbs, and when you combine British spelling ('flavourful') with this adverb marker, you get a word that's correct but rarely written because 'flavorfully' is more common!
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