For Sauce: Melt butter in saucepan over moderate heat and stir in flour. Blend together well. Remove pan from heat and add milk gradually. Return to heat and bring to boil, stirring constantly. Make a sachet of the bay leaf, clove, parsley stalks, and onion. Add to simmering sauce and reduce heat to low; cook for 15 minutes. Season with salt and white pepper. Set aside until needed.
Heat 1 ounce clarified butter in frying pan on high heat. Add livers, season with salt and pepper, and cook until just done. Do not overcook! Stir in 1 1/4 cups white sauce, 1 teaspoon oregano and 1-ounce brandy. Pour into blender and puree. Add 1 tablespoon butter and continue to puree for 4 minutes more. Place in bowl and chill until required.
Cut tenderloin down center, but not completely through. Open steak and beat flat with rolling pin. Spread diced onion on steak and pat down. Cover with 1/2 of pimento and 2 ounces chicken liver pate. Roll steak up. Cover steak with prosciutto and tie string to secure roll, every 1 1/2 inches, or 4 times. Continue this procedure with remaining beef tenderloins. Cut in between strings to separate meat into individual portions, each roll still tied.
Pour 1 ounce clarified butter into large frying pan over medium heat and fry roll-ups, 2 minutes on each side. Remove from pan, cut off strings and keep meat warm on serving platter.
Drain off as much of the fatty juices as possible and add remainder of diced onion saute quickly to meat residue. Pour in red wine and cook down. Add remaining pimento. Stir in remaining fresh butter and parsley. Pour over fillets.
A Specialty of El Tapatio, Guadalajara, Mexico