Prepare your jars and lids that you will be putting your jelly into.
Prepare the mulberries by washing and draining well. Make sure to cut off the stalks of the fruit.
Wash the apples, peel and core, then chop into small pieces.
Place the apples and mulberries into a large, heavy-based saucepan and cover with water.
Bring to the boil, then simmer, mashing the fruit to release the juice.
To remove any forgotten stalks and the seeds of the mulberries by running the mulberry mixture though a food mill or fine sieve.
Pour the pulp and juice of the mulberries and apples into a large, heavy-based saucepan.
Add the sugar and the lemon and whisk over medium heat until the sugar has dissolved.
Bring to the boil, stirring constantly.
Add a dash of butter.
Boil for around 20 to 30 minutes until the mixture reaches gel stage. The mixture will then need to boil and thicken and you will need to stir it frequently so that it doesn’t burn or stick to the bottom of the pot. If you have a candy thermometer, it needs to read 105°C (220°F), though you will need to keep a close eye on the mixture when it starts getting around this temperature.If you don’t have a thermometer, you can use the jam / cold plate test. Before starting your jam, simply place 3 or 4 small plates in the freezer. When you think the jam may be ready, place a small teaspoon amount of jam onto one of the cold plates from the freezer and let it sit for about 30 seconds. Then run your finger through the middle of the blob of jam. If the line starts to fill back over, it means the jam is too runny and is not ready yet, so keep cooking and repeat again in about five minutes. If the line remains, then the jam has reached setting point and is ready.
When done, skim off and discard any foam.
Ladle the hot jelly into hot jars, leaving ¼ in (0.5cm) headspace.
Process in a boiling water bath canner for 10 minutes.
Nutritional information is an estimate and provided as a courtesy. The values may vary according to the ingredients and tools that are used. Please use your preferred nutritional calculator for more detailed information.