Line an 8"X4" loafpan with aluminum foil; butter foil, and set aside.
Combine first 4 ingredients ina 4-quart heavy saucepan. Cook over medium heat, stirring constantly, until mixture comes to a boil. Wash down crystals 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 from heat and cool, 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.