The past tense and past participle of dream are either dreamed or dreamt: "She dreamed a lovely dream last night" or "She dreamt a lovely dream last night." One may say has dreamed or has dreamt with equal correctness. Dreamed is more often used in the United States, dreamt in Great Britain. Both forms of the verb require the preposition of when followed by a verb form ending in -ing: "She dreamed (or dreamt) of taking an exciting journey to Europe."
Dictionary of problem words and expressions. Harry Shaw. 1975.