Prepare a plate, put it into freezer for later purpose

Clean and cut the strawberries into dice (cut off the leaves too)

In medium heat, put together the strawberries and 1/4 part of the sugar into the pan.

Boil and stir them well until the juice comes out, and the sugar completely melt.

Keep stirring and add the rest of the sugar, stir them well until all sugar completely melt.

Skim the white bubbles that appear from this process, and let it boils until the texture become thicker and the color become darker. It takes about 15 to 20 minutes.

Turn off your stove, and take out the plate from the freezer, put about a drop or 2 drops of the jam's liquid onto the plate, and chill it into the freezer about 1 minute.

Check the texture by touching the liquid after being chilled. If the liquid could get a bit wrinkle and thick after being touch, it means the jam is done, but when you touch it the liquid is too liquidy, it means you need to boil it a bit more, until it becomes thicker than before.