Preheat oven to 180°C. Line base and two long sides of a 23 x 33 tin with baking paper.
In a large bowl, whisk caster sugar and eggs for 1 minute until pale and foamy. Whisk in peanut butter.
Add peanut butter, So Good Almond milk, margarine, salt, and vanilla, and whisk again until very smooth. Sift over flour and cornflour, and whisk once more until just combined.
Transfer batter to prepared tin, smooth surface, and bake 18 - 20 min until the cake is golden and a toothpick inserted into the centre comes out clean. Cool in tin for 5 minutes, then turn out onto a wire rack and cool completely.
To make the glaze, place So Good Almond milk in a saucepan over medium heat, warm until just steaming – do not boil. Remove pan from heat, add the chopped chocolate, and whisk until melted. Whisk in cocoa powder and icing sugar until smooth. Transfer glaze to a large measuring jug, or a medium bowl, and cool slightly.
Trim edges of cake and cut into 20 pieces. Combine chopped peanuts and coconut in a small bowl. Using a fork to support a piece of cake, dip base into bowl of glaze, then spoon the chocolate glaze over top and sides to coat evenly. Transfer to a rack or piece of baking paper, and sprinkle top with coconut mixture. Repeat with remaining cake pieces.
For a filled lamington, slice cooled cake into two layers through the centre, spread bottom layer with a thin coating of your favourite jam and drizzle with a bit of extra peanut butter. Replace top layer and continue from Step 6, to coat with chocolate glaze.
If chocolate glaze thickens as you’re coating the cakes, place the jug into a shallow bowl of hot water and stir for a minute or two until it warms up.