For The Filling And Frosting, Place The Sugar And Butter In A Large Mixing Bowl, And Beat With An Electric Mixer On Medium Speed Until The Mixture Comes Together And Lightens.
In A Separate, Smaller Bowl, Beat The Egg Yolks With A Whisk Until They Turn Light Yellow In Color.
Stir The Egg Yolks Into The Butter Mixture Until Combined.
Fill The Bottom Saucepan Of A Double Boiler With 2″ Of Water.
Place The Pan Over Medium-High Heat And Bring To A Boil, Then Reduce The Heat So The Water Simmers.
Turn The Sugar And Egg Mixture Into The Top Pan Of The Double Boiler.
Cook Over Simmering Water Until The Custard Thickens And Is Smooth, Stirring Constantly, 30 To 40 Minutes.
Remove The Pan From The Heat And Stir In The Raisins, Cherries, Pecans, And Vanilla.
Stir To Combine The Ingredients Well, And Then Stir In Up To ½ Cup Of Bourbon, Adding The Bourbon To Taste.
Transfer This Mixture To A Glass Bowl And Cover With Plastic Wrap And Chill Until Ready To Assemble.
It Can Be Made A Day In Advance.
For The Cake, Place A Rack In The Center Of The Oven, And Preheat The Oven To 350°F.
Lightly Grease The Bottom Of Three 9″ Pans With Vegetable Shortening And Flour.
Cut Waxed Paper Rounds To Fit The Bottom Of The Pans, And Place These In The Pans.
Set The Pans Aside.
Place The Soft Butter And Margarine In A Large Mixing Bowl With The Sugar.
Cream The Mixture By Beating On Medium-Low Speed Until The Mixture Comes Together And Lightens, 2 To 3 Minutes.
Add The Eggs, One At A Time, Beating Well After Each Addition.
In A Separate, Smaller Bowl, Sift Together The Flour, Baking Powder, And Salt.
Add The Flour Mixture And Milk Alternately To The Butter Mixture, Beginning And Ending With The Flour Mixture.
Blend In The Vanilla.
Divide The Batter Between The Prepared Pans, And Place The Pans In The Oven.
Bake Until The Cakes Are Lightly Browned And Spring Back When Lightly Pressed In The Center, 25 To 30 Minutes.
Remove The Pans From The Oven To A Wire Rack To Cool For 10 Minutes.
Run A Knife Around The Edges Of The Cakes, Give The Layers A Gentle Shake, And Invert The Layers Once And Then Again Onto The Rack To Cool Completely, Right Side Up, About 30 Minutes.
To Assemble The Cake, Place The Filling Between The Layers And On Top Of The Cake, Leaving The Sides Bare.
Decorate The Top Of The Cake With The Reserved Cherries And Pecans, If Desired.
