Prepare a 7 or 8 inch square baking dish or cake pan, lightly buttering the sides and lining the bottom with parchment or greaseproof paper.
Butter a large heat proof bowl and set aside.
Butter the sides of a heavy saucepan.
In the saucepan off the heat, mix together the sugar, cream maple syrup, butter and baking soda.
Bring the mixture in the saucepan to the boil over medium heat, stirring constantly with a wooden spoon.
Boil, stirring occasionally, until a candy thermometer registers 238°F (114°C). This is the soft boil stage and can also be judged by dropping about a half teaspoon of the mixture into very cold water. The syrup should form a soft ball that flattens when it is removed from the water.
Pour the mixture into the greased wide bowl you prepared earlier. Place the bowl on a rack and let cool in a safe place to 100°F (38°C). This will take about 2 hours.
Transfer the mixture to the bowl of an electric mixer and beat in the vanilla.
Continue to beat the mixture at medium high speed for about 7 more minutes until it is lovely and thick and most of the gloss has disappeared.
Scape into the buttered, parchment lined baking dish or cake pan, smoothing the top.
Place the pan on a rack and allow to cool thoroughly.
Chill in the fridge before cutting into small squares.