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 23
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.