In a medium saucepan, melt the butter. Add the onion powder and beer. Whisk to combine and simmer for about 5 minutes or until the beer has reduced by about half. Whisk in the mustard and continue cooking for 2 - 3 minutes. Remove from heat and transfer to a container to cool. Once cool, whisk in the sour cream. Cover and place the beer mustard in the fridge until you are ready to serve.
for the egg rolls
Brown the sausage, drain and allow to cool. Mix the cooked sausage with the chopped egg, shredded cheese, parsley, mayonnaise, Worcestershire sauce and salt.
Fill each of 12 egg roll wrappers with 3 - 4 tablespoons of the mixture, roll and seal with water.
Heat the vegetable oil in a non-stick pan over medium-high heat. Pan fry the egg rolls for 2 - 3 minutes per side (starting with the seam side down). Being careful not to crowd the pan, only fry 3 - 4 egg rolls at a time.
Rewarm the beer mustard sauce and serve with the Scotch egg rolls.