• 1 large, plump vanilla bean, split open (or 1/2 vanilla bean and 1/2 cinnamon stick)
• 1/2 tsp. baking soda, dissolved in 1 tbsp. water
In a large, heavy pot (not iron) over medium heat, combine milk, sugar and vanilla bean (or vanilla bean and cinnamon stick). Stir regularly until milk comes to a simmer and sugar is dissolved. Remove pot from heat and add dissolved baking soda; it will bubble up at this point, especially with goat's milk. When bubbles have subsided, return pot to stove.
Adjust heat so that mixture is simmering briskly but not boiling. Cook, stirring regularly, until mixture turns pale golden, about 1 hour. You will now need to stir the milk more regularly as it begins to thicken and turns a caramel-brown color. Don't allow the milk to stick to the bottom of the pot. To test for doneness, drop a few drops of cajeta into a small glass of water. If a soft ball forms, cajeta is ready.
If you take pot off stove and allow cajeta to cool, it should be a medium-thick sauce. If it's too thick, add hot water, 1 tablespoon at a time, until it is the proper consistency. If it's too thin, return to the heat until it thickens.