First prepare the caramel sauce recipe by combining the sugar, vinegar & water in a medium heavy bottom sauce pot stirring only until is dissolved not after it starts to boil or you will get crystals in your caramel! The acid helps to prevent this, but it can still happen if you stir after it starts boiling
Watch it carefully as it turns from a light amber to medium amber, take it off the heat when it is medium amber as it will continue to cook & get darker even after you remove it from the heat
Slowly & carefully pour in the room temperature plant milk & add the vegan butter & salt stirring slowly & carefully. Once the bubbling subsides stir it to a smooth sauce
Pour into a heat proof container and refrigerate until needed *it will thicken as it sits!
Divide the caramel sauce into 1 cup for the cake batter / ½ cup for the buttercream & ½ cup for in between the layers
Next preheat the oven to 350F & grease & parchment line your cake pans
Prepare the cake batter by combining the vegetable oil with the melted vegan butter, add the vanilla extract & set aside
Combine the plant milk with the vinegar & let stand for 5 minutes to thicken.
Sift all the dry ingredients together in a large mixing bowl, including the sugar.
Pour the wet ingredients this will be the plant milk mixture & the butter/oil mixture including the cooled caramel sauce into the dry ingredients & whisk smooth about 50 strokes to develop the batter
Pour the batter into the greased and parchment lined pan(s) & bake immediately in the preheated 350°F oven for 15 minutes, then turn the open temperature down to 325°F to bake the rest of the way, approximately 20 minutes more or when you gently press the centers they are springy to the touch. Or do the toothpick test for moist crumbs.
Cool in the pan(s) until you can safely touch without burning yourself then turn the cake(s) out onto a cooling rack to cool the rest of the way.
Meanwhile prepare the buttercream recipe of your choice and at the last stage of mixing add in ¼ cup of that COLD COOLED caramel sauce. Reserve until needed Next prepare the vanilla custard by combining all the ingredients except for the vanilla extract & the vegan butter in a medium sauce pot over medium to high heat & bring to a boil stirring constantly to avoid scorching the bottom .
Once it starts to bubble let it boil on low heat for about 20 seconds.
Remove from the heat & add the vegan butter & vanilla extract & stir until melted & smooth.
Let it cool before attempting to build this cake by layering with sponge cake ½ cup caramel 1 sliced banana then about ¾ cup custard.
Repeat that same layering with the remaining ingredients then ice the cake with the caramel buttercream & garnish with the last of the caramel sauce & Nilla Wafers Cookies