In a large heavy saucepan, combine sugar, flour and salt. Stir in cream; add butter. Cook and stir over medium heat until the butter is melted; bring to a boil. Reduce heat. Simmer, uncovered, for 30 minutes, stirring occasionally. Stir in nuts and vanilla. Cool and set aside.
In a large bowl, beat oil and sugar until well blended. Combine the flour, cinnamon, baking powder, baking soda and salt; add to the creamed mixture alternately with eggs, beating well after each addition. Stir in the carrots, raisins and nuts.
Pour into three greased and floured 9-in. round baking pans. Bake at 350° for 35-40 minutes or until a toothpick inserted near the center comes out clean. Cool in pans 10 minutes before removing to wire racks to cool completely.
For frosting, in a small bowl, beat the butter, cream cheese and vanilla until fluffy. Gradually beat in sugar until smooth. Spread filling between cake layers. Frost the sides and top of cake. Store in the refrigerator. Yield: 16-20 servings.