Rinse the berries and drain in a colander. Transfer to a large stainless kettle or enamel pot. (I prefer one with tall sides that will allow the jam to bubble, and not splash hot liquid onto the stove.) With a potato masher, crush the berries, just enough to release juices, yet not too much. Whole berries add a nice texture to the finished jam.

Add the sugar and stir to combine. Set over medium-high heat and melt the sugar into the berries. Grate the lemons with a zester, then squeeze out the juice. There should be approx. 1/4- 1/2 cup juice. Add to the berries and sugar.

Continue to boil over medium high heat, stirring occasionally with a wooden spoon. About 20 minutes into cooking, set up a candy thermometer and watch it closely until it reaches 220*. This can take up to 30 minutes, so be patient. You may notice the jam turning thicker.

Meanwhile, wash 5 pint-sized jars and prepare lids. Sterilize in the dishwasher, or pour boiling water in to clean and heat. Once jam reaches desired 220*, turn off the heat. Ladle hot jam into jars within 1/4 inch of the rim. Wipe rims clean, before placing jar lids on, the screw on the outer rim.

Flip sealed jars upside down, which will completely seal the rubber lids. Leave for 10 minutes, then flip jars back over to right side. Allow the jars to cool and you will know they have sealed when they make a slight popping sound to invert.

Make a decorative label with your name,  the date and the name of the jam. Store in a cool dark cupboard, ready to use anytime.