From producer's website:
MASSIVE! - LONG BOIL BARLEYWINE
MASSIVE! Barleywine is released every year. What makes this beer so distinctive, and gives it the great depth of flavor, is the 8 hour long boil technique. The kettle at Gigantic is heated by a burner, essentially a blow torch under the kettle. This high heat caramelizes the wort, and the long boil intensifies that caramelization. The recipe changes every year, using different malts and hops, but the technique remains the same.
We also have a bourbon barrel aged version that is released more infrequently.