As a spread on bread, melted into veggies or potatoes, or added to fish or meat...this butter is mustard flavour at its richest.
In a bowl, mash butter with a fork. Add remaining ingredients and mix well.
Spoon onto a sheet of waxed paper and form into a 7-inch (17 cm) log. Wrap well in waxed paper and refrigerate or freeze until ready to use.
As a suggestion for use, soften slightly before slicing off 1/4-inch (6 mm) rounds of mustard butter and place on top of fish or seafood when barbecuing or baking. Just before serving, place another pat of top of each serving and let the heat from the cooked fish melt the butter.