Prepare the berries. Place the strawberries in a saucepan and sprinkle with sugar. Leave for 2-3 hours to let the juice out.
Cook strawberry and mint jam. Place the pan on the stove and simmer the berries. Once boiling, add the lemon zest and juice, stir, and simmer for about 15 minutes. Remove the pan from the heat, let the jam cool slightly. Add the mint and place it back on low heat. Simmer, stirring, for another 10 minutes. Turn off the heat.
Store the jam. Pour the hot dessert into clean jars and roll up the lids. Turn upside down and let cool. Store in the cellar or refrigerator.