Adults: Add 3 g of chaga chunks to 1 litre of water. Simmer for 10–20 minutes to make a tonic, or several hours to make a concentrate. Temperature range should be between 50 and 70 °C; never a rolling boil. Serve hot or let cool to room temperature, then refrigerate up to 14 days. Store used chaga chunks in freezer, and reuse 3–5 times or until water runs clear. After several brews, you may wish to break chaga chunks into smaller pieces to enable hot water to penetrate further and extract more beneficial compounds.