Carefully wash the strawberries, then drain and dry carefully. Using a pairing knife, carefully remove the stems and small green leaves.
Then puree the strawberries with water, minus one tbsp, as well as the sugar, cinnamon and vanilla.
Once pureed, transfer to a small saucepan and add butter and the starch or flour diluted in 1 tbsp water. Place the saucepan over low heat and stir with a wooden spoon. Allow the sauce to thicken as you continue to stir, making sure that lumps do not form.
After ten minutes, once the sauce has a smooth, uniform consistency, remove the saucepan from the heat and let cool. Then place the sauce in the refrigerator and chill for a couple of hours.
Serve the strawberry sauce paired with icecream or pudding.