Lightly grease a 23 x 33 cm (9 x 13 in) ovenproof dish and set aside.
First step: Melt the sugar. In a heavy-bottomed saucepan, melt 500 ml (2 cups) of sugar over low heat. Stir frequently until the sugar is completely liquid, about 20 minutes. Creamy fusion: While the first portion of sugar is melting, combine the remaining 4 cups of sugar and the heavy cream in a large saucepan or Dutch oven. Simmer this mixture over low heat.
Incorporate the sugars: Once the sugar in the small saucepan has completely melted, pour it into the large saucepan while stirring constantly.
Reaching the soft ball stage: Increase the heat to medium and cook the mixture until it reaches a temperature of 118°C (244°F), which is the soft ball stage (a small amount placed in cold water forms a soft ball).
Stir in the baking soda: Remove the pan from the heat. Stir in the baking soda until it is completely dissolved.
