Step 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).

Step 2

In a small bowl, whisk together the milk and eggs until homogeneous.

Step 3

In a separate larger bowl, sift together the gluten free flour, xanthan gum, baking powder, sugar and salt.

Step 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.

Step 5

Add the milk+egg mixture and, using a hand mixer, whisk until you get a smooth cake batter.

Step 6

Evenly distribute the cake batter among the three lines cake tins and smooth out the tops.

Step 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.

Step 8

Leave the cakes to cool in the cake tins for about 10 minutes, then turn out onto a cooling rack.

Step 9

Once cool, level off the cakes if they have domed while baking (the cut-offs make for an excellent snack).

Step 10

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.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.I recommend using a pot with a light-coloured bottom so that you can follow the changing colour of the butter.

Step 11

Allow the butter to cool at room temperature or in the fridge until it firms up but is still "spreadable" (see post).

Step 12

Whisk the cooled and firmed-up brown butter until pale, fluffy and increased in volume.

Step 13

Add the powdered sugar and whisk for a further 4 - 5 minutes until the frosting is smooth and super fluffy.

Step 14

In a pot, melt the sugar on medium-high heat while constantly stirring, until it is a deep golden brown.

Step 15

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.

Step 16

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!)

Step 17

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.)

Step 18

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.

Step 19

Place the popcorn into a large bowl or onto a large baking sheet lined with a silicone mat or aluminium foil.

Step 20

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.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.

Step 21

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.

Step 22

Add the baking soda and mix quickly – the mixture will bubble up so be careful not to burn yourself.

Step 23

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.

Step 24

Allow the caramel covered popcorn to cool, then break it up into smaller pieces.

Step 25

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).

Step 26

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.

Step 27

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.

Step 28

Spread the salted caramel on top of the cake, and allow it to drip down the sides.

Step 29

Pile the caramel popcorn on top of the cake. Use the salted caramel to stick the individual pieces together (to make it more stable).

Step 30

That's it! Enjoy!

Step 31

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.