Aaron Doran was the beneficiary of some poor defending 60 seconds later to double Caley Thistle's lead before Billy McKay completed the scoring with a 59th-minute header.
Butcher said: "I'm delighted. That performance against St Mirren was just a continuation of the displays the boys have been putting in pre-season.
"I would like to take credit for my half-time team talk having an effect, but I can't do that.
"It just seems to be the case at home that the first half of matches, especially in the early part of the season, are tight and tense affairs.
"However, in the second half the game opens up and there's that bit more space for us to operate in.
"The wind didn't help us in the first half either, but we'll certainly take three goals in the second half."