Begin by combining equal parts yellow and brown mustard seeds in a bowl with enough water and apple cider vinegar to cover them completely. Let the mixture soak for 12 to 24 hours at room temperature.

While your seeds are soaking, take a separate bowl and mix together paprika, cayenne pepper, turmeric, and salt. Set this blend aside.

After the soaking period, transfer the softened mustard seeds along with any remaining soaking liquid into a medium saucepan. Stir in your prepared spice blend and your choice of sweetener. Cook over medium-low heat, stirring constantly for about 10 minutes until it thickens slightly.

Remove the saucepan from the heat and let the mixture cool for a few minutes. Then, using a blender or immersion blender, blend to your desired texture.

Allow your mustard to cool completely to room temperature. Transfer it into an airtight jar or container and store in the refrigerator for up to 4-6 weeks.