Wash your strawberries and remove the hull (the green part). Cut the clean berries in half.
Add the strawberries to a large saucepan with the water. Heat gently over medium heat for 15–20 minutes, until the berries soften and release their juice. Stir occasionally, using the back of a wooden spoon to mash the strawberries gently against the side of the pan.
After about 20 minutes, pour the contents through a fine mesh strainer, cheesecloth, or jelly bag into a clean bowl. Let it drip through without squeezing to keep the liquid clear. I like to tie a string around the cheesecloth and hang it on a cupboard handle to let the juice drip through for 30 minutes or so.
You’ll be left with bright strawberry water and a soft pulp. You can use the pulp in baking (I like to freeze it and add it to muffins), or it can be used in jam making.
Add the strained juice back to the pan. Add the sugar, lemon juice, and citric acid. Heat again over medium heat, stirring until the sugar dissolves completely. This should only take a few minutes.
Pour the hot cordial into sterilised glass bottles using a funnel. Add a lid and seal it right away. Let cool at room temperature and then store in a dark place for up to 3 months. It’s best to store it in the refrigerator after opening it.