German potato salad with beer dressing

Boil the potatoes until tender.
Cool slightly, remove the skins and cut into slices.
Fry the bacon until crisp, crumble and mix with the onion and celery. Set aside.
In a small saucepan, stir the melted butter and flour until well blended. Simmer for a few minutes.
Add the mustard and sugar and stir in the beer and Tabasco sauce. Bring to the boil, stirring continuously.
Once the sauce has thickened, adjust seasoning to taste, remove from the heat and stir in the parsley.
Pour the sauce over the potatoes.
Leave for at least 1 hour before adding the bacon mixture.
Mix lightly, season with salt and pepper and serve.
Serves 6.