Begin with mixing the oil with the coarse mustard and while stirring bring this to a boil. Then keep on heating and stir it every now and then to prevent it from burning. Then moisture will slowly vaporize and the mustard will start to fry.
Once the mustard start to color you need to turn down the heat for more control. You want a nice brown color.
Now drain the mustard and press out any oil. Don’t throw this away, it’s packed with mustard flavor and perfect for a vinaigrette or to finish a hollandaise.
Let it cool down and then keep it dry and covered for later.