Preheat oven to 170C (150C fan) / GM 3. Grease a 23 cm / 9inch springform tin with a little oil and line with baking parchment.
Sift cocoa powder into a bowl or jug, whisk in the boiling water til you have a smooth, chocolatey, slightly liquid paste. Stir in the vanilla extract, then leave it to cool a little.
In another bowl, combine the ground almonds, bicarbonate of soda, and pinch of salt.
Beat together the sugar, olive oil and eggs in a bowl til you have a light yellow and thickened cream. I beat by hand, or with an electric hand whisk, but you could do it with a paddle attachment in a stand mixer
Pour in the cocoa mix gradually, beating all the time. Then slowly add the ground almond mix. Stir, then pour into the tin.
Bake for 40-45 minutes until largely set. The centre will still look a little wet. Test with a cocktail stick which should be mostly clean but with a few crumbs on.
Let it cool for 10 minutes on a wire rack in its tin. then ease the sides of the cake with a knife and remove it from the tin.