Preheat oven to 350 degrees. In a mixing bowl, whisk together flour, cocoa and salt until well blended and cocoa clumps have all broken up, set aside. In a small saucepan, melt butter with evaporated milk over medium low heat, stirring occasionally.
Remove from heat and allow to cool slightly (I just did this by whisking it for 1 minute, alternately the butter can be melted in microwave with evaporated milk in a microwave safe bowl in 20 second intervals, stirring after each interval until melted). Pour melted butter mixture into a large mixing bowl and whisk in sugar and vegetable oil.
Add eggs and vanilla extract and mix until well blended. Add in dry ingredients and mix, using a wooden spoon, until combine. Pour and spread batter evenly into a buttered 8 x 8 baking dish.
Bake in preheat oven for 32 - 36 minutes, until toothpick inserted in center comes out with a few moist crumbs attached. Allow to cool for about 15 - 20 minutes before cutting into squares.