You know what’s a scam? Jam.
Specifically, jam prices. Jam prices are a scam.
This recipe yields a LOT and costs very little.
It’s also very easy. Totally not a scam.

{ My grandma’s recipe, via my dad, stored in my muscle memory
since I last made it about 10 years ago. }

Gather:

1kg citrus – I used about 800g blood orange and 200g kumquat¹
1L boiling water
1kg white sugar
A bunch of clean, sealable jars (I used four: 2 large, 2 small)

Then:

1. The night before jam day:
   Cut the citrus – skin and all – into thin, even slices. Scoop out any seeds and set them aside in a muslin cloth or tea strainer, and pop it in the fridge.
2. Put the fruit in a large/heavy saucepan (cast iron is perfect).
3. Boil the water in a kettle and pour it over the fruit, making sure it’s all submerged.
4. Put the lid on and leave it to soak at room temperature overnight.²
5. The next day:
   Put the cloth or strainer full of seeds into the saucepan with the fruit.³
6. Put the saucepan on the stove over a medium/high heat and bring it to the boil, stirring occasionally.
   
7. Once it’s boiling, take out the bag/strainer full of seeds. You can chuck them out now.
8. Carefully pour the sugar into the saucepan – yes, it’s a lot – and stir well.
9. Return to a simmer – uncovered, stirring occasionally – then turn the heat down to medium/low.
10. Leave it to simmer away – yes, stirring occasionally – until it gets nice and thick. This could take an hour or so, so check in every now and then to make sure it’s not sticking on the bottom. To test if it’s ready (“gelled”), drop a bit of the liquid onto a cold plate and let it cool down enough to be touched. If it’s sticky when you drag your finger through it, it’s done. You should also see it gumming up the edges of the saucepan and/or your stirring spoon.
11. Once the marmalade is set, remove it from the heat and immediately (carefully!) spoon it into the clean jars and screw the lids on.
12. Leave the jars to sit on a bench somewhere until they’ve cooled to room temperature. As they cool you should hear them vacuum-seal themselves.
    
13. Serve on fresh buttered bread (I’ll revisit that subject soon!) and a cup of Earl Grey. You can store the unopened jars in the cupboard, then in the fridge once you’ve broken the vacuum seal.

Notes:
¹You can actually use any quantity of any fruit, as long as you use equal quantities of sugar and water. So you could use 750g of lemons, for example, as long as you use 750mls water and 750g sugar.
²This soaks all the bitterness out of the skin and pith, and brings out the pectin you need for the marmalade to set. I don’t know how, it’s just what my grandma did, and it works.
³The seeds are full of pectin, which also helps your marmalade set. Citrus can often set/gel on its own/without the seeds, but I kind of don’t trust it. If you want a less-firm set, you could leave out the seeds completely.