Weigh the oranges to determine the required weight of sugar and liquid.
Squeeze the juice from the halved oranges and remove pips.
Place pips in a cup of water and shred the peel into 0.25cm pieces.
Cover the peel and juice with water and soak both the peel and the pips overnight.
Add the peel, juice, and pip-soaking water to a saucepan.
Tie the pips in muslin, add to the pot, and simmer for 2 to 3 hours until the peel is soft.
Strain the liquid and adjust the volume to 1000ml using water or by boiling it down.
Add 1000g of white sugar, brown sugar, lemon juice, and the cooked peel to the liquid.
Boil the mixture until it reaches 105°C.
Let the marmalade sit for 10 minutes before pouring into sterilized jars.
Seal the jars tightly and allow them to cool completely.