Extol

The verb 'to extol is always (properly) spelled with one '-l' in British English. In American English, it may, according to on-line Fowler, be spelled with one or two '-l's, although Merriam-Webster does not list the spelling with double '-ll-', neither as headword nor as permitted variant.

Extol means 'to praise highly', 'to laud to the skies' and is pronounced 'ex-TOHL' (IPA: /ɛ (or ɪ)k ˈstəʊl/). The inflections have the '-l-' doubled: past forms extolled, present participle extolling. The agent noun is extoller. The noun 'extolment' may be current in American English, but seems to be obsolete in British English. AWE advises you against its use.

Etymological note: extol is from the Latin prefix ex-, here 'upwards', and verb tollere, 'to lift'.

You may also want to see AWE's note on spelling at -l - -ll-.