Remove the bay leaves and juniper berries from the drained vegetables. In a sauce pot over medium heat, add the butter and melt. Add in the flour and caraway seed and make a roux, cooking until golden brown, about 3 – 4 minutes. Slowly pour the remaining reserved beer stock to the roux, whisking to combine. Then bring the mixture back to a simmer, adding in the onions and the liquid smoke. Simmer for about 5 minutes, until the sauce is medium thickness, add in the mustard and adjust seasoning with salt and pepper.