Line an 8"x4" loaf pan with aluminum foil; butter foil and set aside.
Combine first 4 ingredients in a 4-quart heavy saucepan. Cook over medium heat, stirring constantly, until mixture comes to a boil. Wash down crysals from sides of pan using a pastry brush dipped in hot water. Insert a candy thermometer into eggnog mixture. Cook, stirring occasionally, until thermometer registers 238°. Remove pan from heat and cool sugar mixture, undisturbed, until temperature drops to 190° (15 to 18 minutes.)
Stir in pecans and remaining 3 ingredients; beat with a wooden spoon until fudge thickens and just begins to lose its gloss (5 to 8 minutes). Pour candy into prepared pan. Cool completely; cut into squares.