From the brewery:

Following century old recipes all malts made at the Schlenkerla brewery are dried by wood fire. While for the classic “Aecht Schlenkerla Rauchbier” traditionally beech has been – and still is – used, the malt for “Schlenkerla Oak Smoke” is kilned with oak wood. The resulting Oak Smoke Malt has a smoother and more multi layered smoky note than the intensely aromatic Beech Smoke Malt. The hence complex smokiness in “Schlenkerla Oak Smoke” is paired with the multifaceted bitterness of finest Hallertau aroma hops. With 8% alcohol and amber color it matures for months in the deep brewery cellars underneath Bamberg into a special treat for smoke beer lovers for Christmas.