In a large, heavy-bottomed saucepan, combine milk, the Redpath® Granulated Sugar, vanilla extract (or half a vanilla bean that has been split in half and seeds scraped, pod included), and salt. Place over medium heat, stirring occasionally to dissolve the sugar. Bring mixture to a simmer.
In a small bowl, stir together the water and baking soda until dissolved.
Remove the simmering milk mixture from the heat and add the baking soda solution to the pot; mixture will bubble up and become frothy. Keep stirring to prevent the mixture from bubbling over. When the bubbles subside, return the pot to the heat.
Cook on medium heat until mixture returns to a simmer. Reduce heat to medium-low and continue cooking, stirring frequently, until mixture thickens and darkens in colour; 45 minutes to 1 hour. The longer the caramel is cooked, the more intense the caramel flavour will be. Note that the sauce will continue to thicken as it cools.
Remove from heat once the desired consistency and a deep golden brown colour are reached (the sauce is ready when it leaves a clear path on the bottom of the pot and is similar in consistency to maple syrup or thicker).
Carefully remove the vanilla pod if used. Transfer desired amount of sauce to a small dish for dipping and cover loosely with plastic wrap to keep warm. Transfer the remaining sauce into a heat-proof jar or container to cool completely. Cover and refrigerate for up to 3 weeks. Warm up desired amount before using as a dipping sauce.