Take the seeds out of their shells, cut them into small pieces (about the size of coffee beans) and roast them in a pan over a moderate heat while stirring and turning.
After roasting, immediately grind the acorn pieces into a powder in a mortar or coffee grinder and store this in a well-closing jar.
To prepare coffee, bring the water and powder (1 heaped teaspoon per cup) to a boil in a saucepan and cover and simmer over low heat for about 10 minutes. Add milk or cream and possibly a little sugar to the strained coffee.
This very bitter-tasting coffee was used as a substitute for coffee beans, especially in the war and post-war periods. It was also generally considered to be an invigorating drink and effective for some gastrointestinal complaints.