Step 1: Prepare the oranges

Wash the oranges thoroughly. Cut them in half and squeeze out the juice, setting it aside. Remove any seeds and place them in a muslin bag (they contain pectin, which helps thicken the marmalade).

Step 2: Slice the orange peel

Using a sharp knife, thinly slice the orange peels into fine strips. The thinner they are, the smoother the marmalade texture will be.

Step 3: Simmer the peel

In a large pot, add the sliced peels, muslin bag with seeds, and 2 liters of water. Bring to a boil, then reduce to a simmer. Let it cook for 1.5 to 2 hours, or until the peels are soft and translucent.

Step 4: Add the sugar and lemon juice

Remove the muslin bag and squeeze out any juice from the seeds before discarding. Stir in the sugar and lemon juice, stirring until the sugar dissolves completely.

Step 5: Boil to set

Increase the heat and bring the mixture to a rapid boil. Cook for 15-20 minutes, stirring occasionally, until the marmalade reaches 105°C (220°F) on a candy thermometer. If you don’t have a thermometer, do the wrinkle test: spoon a little marmalade onto a cold plate, let it sit for a minute, then push it with your finger. If it wrinkles, it’s ready.

Step 6: Jar the marmalade

Turn off the heat and let the marmalade sit for 5 minutes. Pour into sterilized jars while still warm. Seal tightly and let cool completely before storing.