Preheat oven to 180°C/350°F (160°C fan-forced). Lightly oil spray or butter grease two 38 × 25 cm / 10 x 15" baking trays that are 2.5 cm / 1" deep (jelly roll pans). Line with a sheet of baking paper. (Note 6)

Batter - In a large bowl, whisk together the pumpkin and Wet ingredients. Add the Dry ingredients and whisk well until combined.

Fill trays - Divide the batter between the trays (735g batter each). Spread out to the edges using a spatula then tap the trays on the counter (assertively!) to spread the batter out as evenly as you can.

Bake 15 minutes or until a toothpick comes out clean.

Cool for 10 minutes. Invert onto cooling racks then cool completely (1 hour+) or refrigerate overnight.

Cut - Invert a piece of cake onto a cutting board. Cut in half lengthways. Trim as needed for level, even layers. Cover each piece of cake with its own sheet of baking paper (trimmed to size), with overhang for ease of handling.

Platter - Assemble on the platter you intend to serve it on (moving once assembled is hard / risky).

Frosting amounts to use - one-fifth between each layer, and two-fifths for the top and sides.

Layering - Use the paper to transfer one piece on the cake platter. Spread with one-fifth of the frosting, sprinkle with about 1/4 cup of pecan toffee crumble. Top with another layer of cake (invert using paper, or use 2 long offset spatulas/knives/rulers to handle). Repeat twice more with frosting and pecan crumble.

Frost surface - Spread the top and sides with remaining frosting. Sprinkle the surface with remaining pecan crumble.

Refrigerate for at least 1 hour (to stabilise a bit) then cut slices to serve! Use extra pecan crumble for serving, if you want (I want!).

Toast nuts - Preheat the oven to 180°C/350°F (160°C fan-forced). Spread the nuts on a tray and roast for 10 minutes. Remove and let cool for at least 5 minutes.

Toffee - Spread the sugar in a large saucepan over medium low heat. Leave it until you see the edges melting into a clear sugar syrup, then use a chopstick to stir every now and then to encourage the sugar to fully melt. Once it turns pale golden, remove from heat (it will go more golden in the next step).

Work fast - Add the pecans and salt into the toffee. Use a rubber spatula to quickly coat. Spread onto a baking paper lined tray as best you can before the toffee starts to firm up (don't worry if you can't though, we're chopping it up).

Cool and chop - Cool for an hour until the toffee hardens. Break into large chunks then use a knife to chop it into small pieces and toffee pecan dust (this is really nice!). Set aside until required.

Cream butter - Place the cream cheese and butter in a bowl. Beat for 2 minutes on medium high until smooth and fluffy. Use the paddle attachment if using a stand mixer.

Add the icing sugar in 3 batches, starting the beater on low after each addition, to avoid a snowstorm. Scrape down the sides as needed. Once the icing sugar is mixed in, add the vanilla and salt. Turn the beater up to high and beat for 1 minute.

Use immediately, or refrigerate until required, even overnight, though you'll need to bring it back to room temp if it chills and hardens, and give it a good beat to re-fluff.