Caramel Apple Spice Cake

This cake is ridiculous.  Really really ridiculous.  I cobbled it together from several recipes and from some determination to bring together elements that I thought should be a cake, but didn't seem to be a recipe anywhere.  Some parts work better than others; the frosting, though delicious, is terrible to work with because it is sticky and has a silly-putty kind of consistency that won't stick to the cake well.  Still, it's totally worth the fussiness.

First you make THIS SPICE CAKE RECIPE, through step three.  Then stop.  To be honest, I added about 50% more of each spice than the recipe calls for, but other than that, I didn't fiddle with it.  I know... I couldn't believe it either.

Here's where it gets interesting:

Nouns:
Filling-
2 apples, peeled, cored and sliced thinly
2 tbsp brown sugar
1 tbsp butter
1/4 tsp cinnamon

Icing:
2 sticks butter, room temp
4-5 cups powdered sugar, sifted
1 cup sugar
1/4 cup water
1 tbsp corn syrup
1/2 cup heavy cream
1/2 tsp sea salt
1 tsp vanilla extract

Verbs:
Filling and Icing--
In a small saucepan, cook the apples, brown sugar, butter and cinnamon over medium-low heat until apples are soft.  Reserve the apples until you are ready to assemble the cake.  Then, in a clean saucepan, boil the water, sugar and corn syrup without stirring for 5-10 minutes until it is a deep amber color, taking care not to scorch it.  Using a HEAT PROOF spatula, carefully avoiding the hissing splattering, stir in the heavy cream and sea salt.  Now you have caramel sauce.  Set it aside to cool.  If you feel like it, you can add a tablespoon or two to the apples.  Why not?

In a stand mixer, beat the butter until creamy.  Gradually add the powdered sugar and beat to combine.  Gradually add the caramel while beating the icing until it reaches the desired level of caramelly flavor.  If the consistency is too soft, add more powdered sugar.  If it is too stiff, add more caramel sauce or some heavy cream.  Feel free to reserve some caramel sauce to drizzle over the top of the finished cake, or into your mouth, or whatever.

Assembly:
I like to freeze my cake layers for an hour or two up to a day or two before I assemble the cake.  I find it's easier to work with and I get fewer crumbs in my icing.  In any case, the layers should be cooled before assembly.  Set the bottom cake layer on a small dollop of icing on your cake platter, so it stays put.  Then, pipe a ring of icing around the top edge of that layer.  Spread the apple filling inside that ring of icing until even.  Set the top layer over the filling on the ring of icing so that the filling is sealed in and won't goo everywhere while you are frosting this thing.  Spread the icing in a thin layer over the whole cake.  Freeze for 30 minutes.  Then frost with the desired frosting effect.  feel free to just glob it on there, or to get fancy.  I got fancy, but I'm a fancy kind of girl.  I also put some caramelized sugar frou-frou on top of mine, because I love frou-frou.