Combine flour, sugar, cocoa powder, baking powder, baking soda, and salt in a large bowl. Sift and whisk well.

Whisk oil, milk, vanilla extract, and eggs until smooth. Add 1 cup boiling water, mix in gently.

Mix wet into dry, and bake at 175 °C for 35 minutes.

For icing, cream butter till smooth. Add cacao powder, sugar, and a little milk. Add vanilla and salt. Optionally, espresso powder.