Salted Caramel Popcorn Cake

This salted caramel popcorn cake will blow your mind and set off
fireworks on your tastebuds. With pillowy soft peanut butter sponges,
insanely delicious brown butter frosting, an overabundance of salted
caramel and a small mountain of caramel popcorn. Plus, it’s gluten free.
Sounds rather perfect, doesn’t it?

Ingredients

• For 3 x 6 inch gluten free peanut butter sponges:
• 3/4 cup + 1 tbsp (190 mL) milk
• 6 eggs
• 3 1/3 cups (400 g) plain gluten free flour blend (I’ve used a simple
  store-bought blend of rice, potato and maize flour with no added xanthan
  gum)
• 3/4 tsp xanthan gum
• 3 tsp baking powder
• 1 3/4 cups + 2 tbsp (375 g) white sugar
• 1/2 tsp salt
• 1 stick (113 g) unsalted butter, room temparature
• 7/8 cup (225 g) smooth natural peanut butter, room temperature/soft

For brown butter frosting:

• 4 sticks (450 g) unsalted butter
• 2 3/4 cups (350 g) powdered sugar
• pinch of salt

For salted caramel:

• 1 1/2 cups (300 g) white sugar
• 3/4 stick + 1 1/2 tbsp (105 g) unsalted butter
• 3/4 cup + 1 1/2 tbsp (200 mL) double/heavy cream
• 1/2 – 1 tsp salt

For caramel popcorn:

• 6 cups (115 g) popcorn
• 3/4 cup (150 g) white sugar
• 3 tbsp water
• 2 tbsp (30 g) unsalted butter
• 1/2 tsp baking soda

Instructions
For 3 x 6 inch gluten free peanut butter sponges:

1. Pre-heat the oven to 355 ºF (180 ºC) and line three 6 inch round cake baking tins with baking/greaseproof paper (see post).
2. In a small bowl, whisk together the milk and eggs until homogeneous.
3. In a separate larger bowl, sift together the gluten free flour, xanthan gum, baking powder, sugar and salt.
4. Add the unsalted butter and peanut butter. Using a hand mixer, whisk the butter into the dry ingredients until you get small, pea-sized pieces.
5. Add the milk+egg mixture and, using a hand mixer, whisk until you get a smooth cake batter.
6. Evenly distribute the cake batter among the three lines cake tins and smooth out the tops.
7. Bake
   in the pre-heated oven at 355 ºF (180 ºC) for 40 – 45 minutes or until
   an inserted toothpick comes out clean and the cakes are golden brown on
   top.
8. Leave the cakes to cool in the cake tins for about 10 minutes, then turn out onto a cooling rack.
9. Once cool, level off the cakes if they have domed while baking (the cut-offs make for an excellent snack).

For brown butter frosting:

1. First,
   brown the butter by first melting it in a pot with tall sides and then
   cooking it for about 10 – 15 minutes with frequent stirring, until it
   goes a deep brown colour and starts smelling nutty. The butter will
   foam, so make sure you use a deep pot.
2. Once the butter goes a dark brown butter, remove it from the heat immediately (otherwise it will burn) and pour it into a mixing bowl.
3. I recommend using a pot with a light-coloured bottom so that you can follow the changing colour of the butter.
4. Allow the butter to cool at room temperature or in the fridge until it firms up but is still “spreadable” (see post).
5. Whisk the cooled and firmed-up brown butter until pale, fluffy and increased in volume.
6. Add the powdered sugar and whisk for a further 4 – 5 minutes until the frosting is smooth and super fluffy.

For salted caramel:

1. In a pot, melt the sugar on medium-high heat while constantly stirring, until it is a deep golden brown.
2. Add
   the butter, and mix well until the butter has melted and is fully
   incorporated into the caramel. (Be careful, as the caramel can bubble
   strongly on the addition of butter!) Allow to cook for 2 – 3 minutes.
3. Add
   the double/heavy cream in a slow stream, all the while mixing
   vigorously. (Be careful, as the caramel can bubble strongly and release
   steam on the addition of double cream!)
4. Spoon out a small amount
   of the caramel sauce, allow it to cool, and check its consistency. If
   it’s too thick, you can add a bit more double/heavy cream, and repeat
   the process until you reach the desired consistency. (The salted caramel
   should be quite runny because it will be used for drizzling, but not
   too much otherwise it will drip all the way down the cake.)
5. After
   the final addition of the double/heavy cream, add the salt and allow
   the salted caramel to cook for 1 minute, then remove from heat and allow
   to cool completely.

For caramel popcorn:

1. Place the popcorn into a large bowl or onto a large baking sheet lined with a silicone mat or aluminium foil.
2. In
   a pot, mix the sugar and water, and cook on medium-high heat while
   constantly stirring, until it is a light amber/golden colour. Don’t let
   the sugar go all the way to a deep golden brown.
3. The reason for
   adding the water here (unlike for the salted caramel sauce) is that we
   want a more controlled caramelisation of the sugar, as the caramel can
   burn quickly once the baking soda is added.
4. Add the butter, and
   mix well until the butter has melted and is fully incorporated into the
   caramel. (Be careful, as the caramel can bubble strongly on the addition
   of butter!) Allow to cook for about 30 seconds.
5. Add the baking soda and mix quickly – the mixture will bubble up so be careful not to burn yourself.
6. Quickly
   pour the bubbling caramel over the popcorn and quickly mix the popcorn +
   caramel together. Working fast is crucial at this stage, as the caramel
   gets hard very quickly, and we want all the popcorn covered in an even
   thin layer of caramel.
7. Allow the caramel covered popcorn to cool, then break it up into smaller pieces.

Assembling the cake:

1. Assemble
   the cake by spreading a generous layer of brown butter frosting on top
   of a peanut butter sponge. Drizzle with some salted caramel. Then repeat
   with another layer (see post).
2. Place the third and final peanut
   butter sponge of top. Use the remainder of the brown butter frosting to
   cover the top and sides of the cake. Smooth out the frosting with an
   icing smoother.
3. Refrigerate the cake for about half an hour.
   This will firm up the frosting and ensure that it will stay neat once
   the salted caramel is drizzled on top.
4. Spread the salted caramel on top of the cake, and allow it to drip down the sides.
5. Pile
   the caramel popcorn on top of the cake. Use the salted caramel to stick
   the individual pieces together (to make it more stable).
6. That’s it! Enjoy!

Storage:

• The
  salted caramel peanut butter cake keeps well in the fridge in a closed
  container (or carefully wrapped in cling film) for 3 – 4 days.