Preheat oven to 350°.
Combine flour, sugar, cocoa, baking soda, and salt in a bowl and set aside.
In a separate bowl, whisk eggs together and then add syrup and vanilla.
Combine wet and dry ingredients and mix with an electric mixer.
Line two 6" cake pans with cake liners* and then pour batter evenly into the pans.
Place pans in the oven and bake cakes for 25-30 minutes or until a toothpick comes out clean. Leave cakes in the pans for 10 minutes before carefully inverting them onto cooling racks. Wait until cakes have completely cooled before icing them.
For the icing: combine chocolate and oil in a saucepan over medium heat, stirring occasionally until chocolate has melted; set aside.
Add butter to a bowl and then pour the melted chocolate overtop; let this sit for 3 minutes or so, then mix with an electric mixer before adding the powdered sugar. Continue mixing until icing has formed--icing should be fairly thick. If it seems too thick, add the milk.
To assemble: Once cakes have cooled, use a serrated knife to cut off the domes of the cakes. Ice one of the cakes and then place the other cake on top. Ice the top of that cake and then spread icing all around the cakes until it's covered to your liking.