I found an alternate recipe: (I think it's easy enough to figure what the ingredients are but if you need a translation, let me know.)
BTW: c.a.s. are tablespoons
1 c.a.s de persil
2 gousses d'ail
2 filets d'anchois
1 c.a.s de Worcester[emoji]8482[/emoji] sauce
1 c.a.s de moutarde forte
1 c.a.c de curry de madras
1 pincée de thym
1 pincée de marjolaine
1 c.a.s de sauce soja Kikkoman[emoji]8482[/emoji]
150 gr. de beurre
150 gr. d'Astra[emoji]8482[/emoji] 10%
The original recipe is a closely guarded secret. The butter was created to lauch a unique concept in the food industry: a single item menu. In the case of Café de Paris in Geneva, it was the entrecôte. Any recipe that you find will be an imitation. Sad isn't it?
Someone was asking about it somewhere else, I can't remember where.... epicurious maybe? Tried to find it and only came up with one or two. Figured someone here would have an idea or two. I probably won't do anything with it unless I find more info on people who have actually tasted versions themselves and volunteer their opinions.