In large pan melt butter, then add flour and quickly stir with whisk to combine and remove clumps. Turn off heat.
Clean, trim stems of Brussels sprouts. Cut in half and keep all of loose leaves. Fill medium stock pot half way with water, bring to boil. Add Brussels sprouts, stirring in hot water and blanch quickly for about 2 minutes or until they turn bright green. Immediate drain. Do not cook Brussels sprouts and make them soft!