I would just do the icing. I've read and seen more than once where brewed coffee really brings out the chocolate flavour.

The coffee is just there to goose the chocolate. Put it in the cake. If you want mocha icing, you can add it to that too, but being careful of total liquid and intensity.

I like the "Best Chocolate Cake Ever" at Add A Pinch, which is a boiling water version. It's also good without the coffee. I use Valrhona cocoa powder, which makes for a very chocolatey, fudgy cake. For a standard layer cake, she uses a teaspoon of espresso powder. (ETA--in the linked buttercream recipe, she also uses ½ tsp. espresso powder, but I don't like the consistency of this buttercream recipe or the espresso in it.)

I would use a coffee mousse filling with a chocolate cake and a mocha icing.

I would love to do a mousse - if it's dairy free :(. Four of us can't have dairy. Great. I will go for the coffee icing/frosting. Thanks.

I would put a tad in both.

I also would put some coffee in the cake and the frosting.

I made a chocolate bundt cake today and used 1/2 cup of leftover brewed coffee instead of plain water. No real taste of coffee at all, but it seems to intensify the chocolate. To taste the coffee, definitely in the frosting.

If I have to need a hint of coffee in the cake then I will try to do that in the icing as I want to keep the chocolate flavor more.

What a coincidence. I made black bean brownies this morning and added 1 tbsp of instant coffee (find grind espresso) and choc chips because I didn't feel like making an icing. Definitely has more coffee flavour to have a coffee icing. I barely notice it in the cake on it's own. I forgot I even asked this question.

The chocolate cake recipe I have posted here has a cup of strong coffee in it but no coffee flavour that I’ve ever tasted or that others have commented on (and I’ve literally made hundreds over the years as I baked professionally). If you want a touch of coffee flavour, put it into the icing.

have always used taster's choice instant granules in the cake ... don't like it as drinking coffee but it brings flavor to cakes, chilis and BBQ sauce ....

For a noticeable coffee flavor, you will likely need to use an espresso freeze dried crystal ‘powder’ — something like ~ Medaglia D’Oro. I’ve made a delicious chocolate layer cake (strong 1-2 liquid oz coffee into the cake mix and then with chocolate ganache frosting. The coffee flavor in the cake was not particularly detectable, even though the cake was delicious and pretty.

Oops! Whopper size! I don’t get a commission, honestly!

That recipe that Plllog refers to "the best chocolate cake ever" really is the best chocolate cake ever. I found that recipe a few years ago and haven't used any other one since.

When Tyler Florence had his 'best of/ultimate' show, I snagged the flourless choc cake recipe. Still like it a lot.

I did substitute dutch chocolate for a portion of the chocolate ... like half cocoa powder-half melted. Melted chocolate last.

it is a fave birthday cake recipe of the family.

flourless chocolate cake