I would like your advice...

[momoreg]

Myky,
There may have been other mistakes, but the most obvious is that you left the mix to stand. The baking soda and cocoa powder begin to react with one another as soon as liquid is added. The carbon dioxide that is produced would normally have aerated the cake in the oven, but instead, it escaped, causing the cake to fall.

[kuan]

I don't get the hot water part of the recipe. We were always told that when using bp/bs you want to keep the batter cool so the leavening agents don't activate.

[palomalou]

My very humble 2 cents: perhaps if the item is mixed and then goes into the oven IMMEDIATELY after adding the hot water it works. That is how the cornbread recipe I use does it.

[BonMaria!]

I always use the Wilton Baking strips dipped in cool water before baking any cake 10 inches and larger. (I also use the Wilton Heating Core).

Here's to Great Baking!

[bigbuns]

The "mixing for 10 minutes" sent up a red flag for me. Overbeating develops the gluten and will make for a tougher cake, in addition to losing your levening and aeration. It just needs to be mixed until all ingredients are well blended - 2 to 3 min. tops.