The growing demand for sustainable alternatives to petrochemical-based epoxy resins has led to the development of bio-based systems. This study introduces a new synthesis method using betulin from birch bark to produce high-value polymeric resins. A novel betulin-derived epoxide (BOE) was synthesized and combined with epoxidized rapeseed oil (ERO), then thermally cured with seven anhydrides and three thermal initiators. Rheological analysis showed a gel time of 45 minutes, with maximum conversion 84–93% within 75 minutes. Coatings applied to plywood were tested for microhardness and friction, showing a transition from soft to rigid systems based on component content and selection. The study highlights the potential of bio-based epoxy resins as viable alternatives to fossil-based counterparts, offering tailored performance for specific applications.