A spell or ability that counters spells can still target Exquisite Firecraft. When that spell or ability resolves, Exquisite Firecraft won't be countered if its spell mastery ability applies, but any additional effects of the countering spell or ability will still happen.

Check to see if there are two or more instant and/or sorcery cards in your graveyard as the spell resolves to determine whether the spell mastery ability applies. The spell itself won't count because it's still on the stack as you make this check.