Welcome. Today I am going to teach you how to cook an all-natural plant-based comfort food that will make your friends on a diet run like vampires from a wooden stake shop. Strawberry jam.

You can cook cherry jam the same way and any other jam with minimum modifications (adjusting the amount of sugar depending on the sugar in the fruit and adding a bit of water to the mix if the fruit doesn't have enough water).

The algorithm:

1. Find a person you would like to spend a couple hours with.
2. Buy 17 pounds (7 kg.) of strawberries and 20 pounds (8 kg.) of sugar. Get a big enough saucepan to house all the strawberries at once. The proportion is the only important thing. You can just as well buy 1 pound of strawberries and 1.2 pounds of sugar, but please consider that boiling the jam takes the same amount of time and skill no matter how much you cook, though peeling is faster if you have less ingredients. For reference, this is what 17 pounds of strawberries looks like:
   
3. Wash the strawberries and peel the tails off (all the green parts). This is best done the following way: get a colander full of strawberries, wash them in it. Grab a handful of strawberries, tear the tail off one of them, throw the strawberry into the saucepan, discard the tail. Repeat. By the way, this is why you should get a friend for this kind of cooking: sitting alone for hours peeling berries or removing seeds from cherries is sad.
4. Add half the sugar to the strawberries, mix everything, leave the saucepan overnight. The strawberries need to let out juice, so that boiling them will be possible without burning them. If in a hurry, three hours will do it.
5. Put the strawberries on medium fire and boil them for 3 hours. Add a third of the remaining sugar every hour and stir the jam until it dissolves. In general, stir the jam every ten minutes to prevent burning on the bottom of the saucepan. Two problems need to be avoided: too much heat at any stage will cause the jam to boil and foam violently and it will go all over the kitchen. Not enough stirring in the last hour or so will make the jam burn on the bottom of the saucepan destroying the entire batch. This is the kind of boil you are looking for:
6. You can check thickness by getting a spoonful out of the saucepan, putting it on a clean plate and waiting for it to cool down. This will give you an idea of what the end product will be like, but please take into account that it will be thicker. This is what I was aiming for with 3.5 hours of boiling (this kind of jam doesn't flow and can be safely smeared onto a toast):
7. If the amount of jam you are cooking is based on 2-3 pounds of strawberries, it can safely be stored in the fridge. It will keep for two months easily as long the jar is clean—just make sure the jar is closed. If there are more strawberries, then sterilizing and sealing the jars is necessary. I may write about it separately when I'm as bored as I am now, but basically you put recently washed glass jars into a cold oven, slowly raise the temperature to about 160 Celsius (320 Fahrenheit), leave them there until the water evaporates, then take them out. Lids should be boiled for three minutes. After you seal the jars, upturn them and leave them bottom-up to check for leaks. Here, two jars have leaks because of faulty seals (you can see the bubbles) and need to either be re-sealed or eaten in a month or two. Re-sealing requires re-sterilizing everything, including the jam itself.
   

What determines the result

Home-cooked jam tends to blow anyone sugar-deprived away, but in case you need the extra oomph:

1. Quality of the fruit is paramount. Get the best you can, and prioritize aroma strength over sweetness. Sugar will give enough of the latter.
2. Thickness is a matter of taste. 3 hours results in medium thickness. Around 5 hours makes jam that turns to marmalade when cooled but it's tricky to cook without burning. Generally, you are fine as long as it isn't too thin. The jam in the pictures was boiled for 4 hours and it barely flows when I upturn a jar. Always check for thickness as you cook by taking some of the jam and letting it cool in a separate plate.

Adjustments

This is a simple dish, and there is not much to change about it. With more sugar the jam will become sweeter, thicker, and have less fruit in it mass-wise. Boiling the jam longer makes it thicker, sweeter, and more homogeneous. When it gets to marmalade thickness, pieces of most fruit merge together completely. Fruit that doesn't let out juice that well might need a bit of water in the beginning. Generally, you leave it with sugar overnight and then add just enough water to make sure the whole thing is boiling. More water is useless as it will just evaporate, unless you need more boiling time for the fruit to dissolve.

Trivia

Jam is boiled so long that every vitamin that can be destroyed thermally is destroyed. It is mostly sugar, so talking about nutritional value is kind of redundant—just don't eat too much. It is also vegan, which I find hilarious considering how unhealthy it is in large doses. Good news is that thick home-cooked jam has more weight to it than you would expect from a carbs-dominated food.

Best eaten with toast and tea or milk during breakfast.