u/Red-lipped-classic

I would like to make a s’mores coffee cake with a crumb like layer for my birthday. I’m struggling to find the right recipe. I’ve never made any of these individually so I’m just wondering would it be as simple as adding an instant coffee to a chocolate cake recipe? Or would that mess up the mix? Also for the crumb layer I was thinking instead of a butter/ cinnamon mixture that I would use ground up graham crackers instead? Lastly, I want the top layer to be gooey like a melted marshmallow. Would it be easier to take a fluff and melt it or take minni marshmallows and melt them? If anyone has thoughts I’m open to them. I’m a decent baker I’m just bored with plain and German chocolate cakes lol 😂