Four Roses is unique among bourbon distilleries in producing ten distinct bourbon recipes from two mash bills and five proprietary yeast strains. OESK uses the ‘E’ mash bill (75% corn, 20% rye, 5% malted barley) with the ‘K’ yeast strain, known for imparting baking spice character. Released in 2025 as part of the new Single Barrel Collection alongside OBSF, OESO, and flagship OBSV. Bottled at 100 proof. Each single barrel expresses its own variation on the recipe. For bourbon drinkers who want to understand how yeast shapes flavor.