Hertog Jan's Vatgerijpte Gerstewijn is a distinctive barrel-aged barleywine from their Proeftuin series. Based on their Grand Prestige, this beer spent eight months maturing in American white oak brandy barrels from California, developing deep reddish-brown character.

The barrel aging imparts notes of bourbon, wine, apple and peach alongside toasted oak character. On the palate, sweet alcohol blends with coffee and caramel notes, finishing with refined bitterness. At 11.6% ABV, this is a considered, full-bodied barleywine best enjoyed slowly at cellar temperature (10–12°C).