Christine Ferber is not as well known in the English speaking world as I believe she deserves to be. The grand-dame of French jams and preserves, she has worked as a chef patisserie with big names of French cuisine such as Alain Ducasse, the Troisgros family, and Antoine Westermann. Rumor has it that celebrities like Brad Pitt are willing to travel half the world to learn the art of jam making from her. Her jams are to be found in high end food stores across France (and on her own website) and she’s known for original flavor combinations that focus on local history and ingredient availability.
I believe one of the reasons her jam recipes are not as well known outside the French speaking world is because her method of working is very closely related to slow food. Her jams are made in a two day process involving maceration and two different boils on different days. This slow process allows the flavors to develop while the fruits slowly release their juice.
The English language uses the word “jam” as a general catch all for fruit preserves, whether the fruits are in pieces or passed through a food mill. Most of Christine Ferber’s recipes are for what the French call “confiture”. In her book, Lecons de confitures (which I cannot recommend enough; I picked the French version while in France but a quite similar one is also available in English), she makes a distinction between confiture (with pieces of fruit) and mermalade (without pieces, processed through a food mill). This recipe for plumb jam should be more appropriately called “confiture” since the fruit is roughly chopped in pieces and not pureed.
The plums I used in this recipe are Reine Claude Verte (Queen Claude Plums), also known as Greengage in English. They are a bit acidic with a very nice honey-like sweetness that makes them ideal for jams or preserves. These plums, while technically a French varietal, have been cultivated with varying success in The Netherlands (and across most of Northern/ Western Europe) since the 19th century.
This recipe makes around 6 250 ml/ half pint jars.
What you need
1.2 kilos/ 3 lbs of Reine Claude plums (to yield 1 kilo/ 2.5 lbs of clean fruit)
850 grams/ 1.8 lbs of sugar
Juice of half a lemon
On the first day:
Clean the plums, cut them in quarters and remove the pits.
Place them in a wide pan (if you do not have a jam making pan, a soup pan with a wide mouth will do). Cover them in the sugar and the juice of half a lemon.
With a wooden spoon, stir gently to mix the sugar, lemon juice and fruit. Cover with a lid and let it macerate for one hour.
After one hour, bring the pan to a boil over medium heat while stirring gently with a wooden spoon. The purpose of this boil is to allow the sugar to dissolve completely. As soon as the mixture begins to simmer, remove it from the heat, cover it with a lid and let it cool completely.
If you have space in the fridge, place the pan in the fridge overnight. In fairness, I usually do not have sufficient space in the fridge to hold a big ass pan so I let it be on the counter. However, the temperature in Amsterdam is never so hot that fruit and sugar would spoil in a few hours.
On the second day
Prepare your canning jars and lids. I usually run the jars in the hot cycle of the dish washer to disinfect them/ wash them thoroughly and boil the lids for five minutes in a sauce pan.
Bring the pan with the fruit to a boil over medium heat. Stir gently with a wooden spoon. The gentle stirring is necessary so that the fruit is not mashed during cooking. Once the fruit mix is boiling, lower the heat to medium low to prevent scorching.
Now comes the part where I believe recipes for making jam can get tricky. This is where I tell you to continue stirring gently for another five to ten minutes. In reality, I do not know how long it will take for the jam to be ready because that depends on a number of factors such as the type of pan, the ambient temperature, the heat source, etc etc. Instead, my very strong advice is to get a food thermometer, stick it in the pan and continue stirring gently until the jam has reached a temperature of 105 degrees Celsius/ 220 degrees Fahrenheit. This is the setting point for jams at sea level, when the natural pectin in the fruit kicks in and you end up with a jelly like texture that is wonderful on a slice of bread.
Fill in the jars leaving 1 centimeter/ roughly half an inch of headspace. Clean the rims of the jars and screw in the lids.
Process the jars in a boiling water canning pan for 5 minutes (at sea level; adjust processing time according to your geographical situation). Let cool completely on the counter.