I recently became brave enough to try making a roux, and of all the times I've made roux, it hasn't gotten very dark. Made a gravy the other night, and was trying to get the gravy to be a dark brown since it was a beef gravy, but after 20 minutes of constant whisking, it was only a yellowish color, sort of like Dijon mustard. The gravy turned out OK, but I know it would've been better with a darker roux. Anyone out there have any advice for a newbie cook?