Preheat the oven to 180°C and line a rectangular cake tin with oil and parchment paper.
In a bowl of a stand mixer fitted with a whisk attachment, add the oil, eggs, and sugar. Beat at medium-high speed until well combined.
Sift together the flour, cocoa powder, salt, and bicarbonate of soda. Add the dry ingredients to the egg mixture, and beat at medium speed until just combined.
In a jug mix together the milk, brewed coffee, and vanilla. Slowly pour this into the egg and flour mixture, with the motor running at low speed. Scrape down the sides of the bowl and mix again. Ensuring the cake batter is well mixed and lump free.
Pour the cake batter into a prepared cake tin and bake in a preheated oven at 180°C for 40 minutes or until a skewer inserted into the center comes out clean. Once baked allow the cake to cool in its tin for 20 minutes and then transfer it to a wire rack to cool completely.
Chocolate Cream Cheese Frosting
Add the icing sugar, cocoa powder, and butter to a bowl of a stand mixer fitted with a paddle attachment. Beat at medium speed until combined.
Add the cubed cream cheese and beat again. Scrape down the sides of the bowl and beat again until light and fluffy. About 5 minutes. Add the vanilla and milk and beat again.
Top the sheet cake with the frosting and smooth it across the cake with a knife or rubber spatula, decorate with m&ms or other candies.