Heat the veloute in a medium saucepan and simmer until reduced by ¼, stirring occasionally. Pour the cream into a metal bowl and temper by slowly incorporating a small amount of the hot veloute. Slowly stir this into the sauce, and return to a very low simmer. Swirl in the raw butter until melted, then season to taste with salt, pepper and lemon juice. Strain through cheesecloth.