- Butter an 8-inch (20 cm) square pan. Line the bottom with parchment paper, letting the paper hang over two sides of the pan.
- In a heavy-bottomed saucepan, bring the cream, brown sugar, sugar and salt to a boil, stirring to dissolve the sugar. Clean the sides of the pan with a wet brush to remove any sugar crystals, if needed. Attach a candy thermometer in the centre of the pan and simmer over medium heat without stirring until the thermometer reads 237°F (114°C) (see note). Remove from the heat and add the vanilla, without stirring.
- Place the pan in a cold water bath. Let cool, without stirring, until the thermometer reads 110°F to 122°F (43°C to 50°C), about 20 to 30 minutes.
- Remove the pan from the water. With a wooden spoon, stir vigorously until the mixture loses its gloss but is still soft, about 3 to 4 minutes.
- Pour immediately into the prepared pan and spread with a spatula. Cover with plastic wrap and press to smooth out the surface. Let cool for 1 hour at room temperature or 30 minutes in the refrigerator. Remove from the pan and remove the plastic wrap. Cut into 1-inch (2.5 cm) squares.
- Cream fudge will keep in an airtight container and freeze well.
If the vanilla is added during cooking, it will lose its flavour.
You can also use a digital thermometer equipped with a probe. Just drop the probe into the syrup.
For a firmer fudge, continue cooking until the thermometer reads 240°F (116°C).
The cooled syrup is very thick. Stirring it takes elbow grease! The syrup will begin to set suddenly. Do not stop stirring until you spread it in the pan, or it could seize in the bowl.
If desired, add toasted and chopped walnuts just before stirring. You can also substitute the vanilla for maple extract.