Beat butter and cream cheese in a large bowl at medium speed, about 2 minutes or until soft and creamy. Gradually add sugar, beating for 2 minutes. Add eggs, one at a time, beating just until yellow disappears. Combine flour and salt. Gradually add flour mixture to butter mixture, beating at low speed just until blended.
Stir in vanilla. Pour batter into 3 greased 8x4 loaf pans. Gently swirl knife through batter to remove air pockets.
Bake at 350 for 45 minutes. Reduce temp to 300 and bake 15-20 additional minutes or until done. Cool in pans 10-15 minutes; remove from pans, cool completely.
Chocolate cream cheese. Bake at 325 for 1 hr 50 minutes.
Marbled cream cheese- Spoon 2 c plain batter into prepared pan; topwith 1/2 chocolate mix; repeat layers. Gently swirl with a knife to create marbled effect, Bake at 325 for 1 hr 30 minuts.