The end result is like a stone-ground, grainy mustard with my cheap stick blender; I got a more powerful stick blender for Christmas, so I'm curious to see if the texture is more uniform on the next batch of mustard. But rustic mustard as pictured here is great, too! I also still buy cheap yellow mustard because I think it does have its place in some recipes.
Soak overnight (I do this in the glass jar I'm planning to keep the mustard in):
1 cup mustard seeds, yellow and/or brown
3 cups water
In the morning, drain off water.
5 tsp. salt
1 cup vinegar (I use white wine vinegar usually)
Blend with immersion blender or stand blender. Presto: mustard!! Keeps indefinitely in fridge as long nobody double dips with a dirty spoon.