Blend together butter, lard, dairy sour cream, brown sugar, baking soda, salt and vanilla. Add flour and oats and mix well.
Divide dough in half. Shape each part in a roll 2" in diameter. Wrap in foil or waxed paper and refrigerate overnight, or at least 8 hours. (For faster chilling place in freezer.)
To bake, cut dough in ⅛" slices; place about 1" apa