In a saucepan over high heat, bring the vinegar to a boil. Remove from heat and add the mustard seeds, bay leaf, and cinnamon stick, stirring to combine. Cover the saucepan and let the mixture rest at room temperature for about 1 hour. The seeds will absorb the liquid.
Remove the bay leaf and the cinnamon stick, scraping off any clinging seed. Add the water, sorghum syrup, and bourbon to the mustard seeds and stir, and then scrape the mixture into the carafe of a blender. Blend until smooth, then add the sweet potato purée and blend until you have a nice cohesive, smooth paste. You can add a few drops of water as you go if you need to get things moving.
Pour the mixture back into the pan and heat over medium heat, bringing it to a boil. Reduce the heat to medium-low and continue to boil gently for approximately 5 minutes, stirring frequently to prevent scorching. Whisk in the sugar, dry mustard, paprika, and salt. Continue to simmer over medium-low heat, cooking the mixture until it has reduced a bit and is thick and spreadable. This should take about 10 minutes.
Cool the mustard in the pan, and then scrape it into an airtight container. The mustard will keep for about 2 weeks in the fridge.
*To make things quicker, I happily use canned plain, all-potato, sweet potato purée, not sweetened or seasoned. I find it at better markets such as Whole Foods. If you can’t find it, wrap a sweet potato in foil, bake until soft (about 1 hour), then blend the flesh with a little water to make a very smooth purée.