In a cast iron skillet, toast mustard seed over medium-high heat until brown and mustard seeds start to pop.
Add toasted and non-toasted to mustard seeds together in a non-reactive bowl.
Add vinegar, turmeric and allspice to mustard seed mixture. Rest on counter for up to 24 hours allowing mustard seeds to soak in vinegar. For the first 6 to 8 hours check frequently and add more vinegar if necessary.
Set pellet grill to 160 °F (and smoke level 10 smoke if available) for 2-6 hours depending on the smoke profile you want.
Add mustard to food processor, blend to desired texture add additional liquid for desired texture.
Add salt and blend
Let rest in fridge for 7 days taste and salt to taste if needed.