I am trying to create a few new recipes and I am stuck on what other ingredients (flavours) would go well with espresso in a baked item.
You may want to consider flavors that are existing compliments to coffee. Think of the many syrups that are available at your local coffeehouse. Things that easily come to mind are chopped hazelnuts or almonds, caramel frosting/icing, cinnamon and nutmeg as spices, chocolate chips or cherries.
Here is an answer to a similar question that covers some of the basics leading to the details below.
Here is a flavor wheel that has been used in particular by Whole Latte Love, created by Ted Lingle of the SCAA (and sold by them) for the purpose of cupping:
According to FoodPairing, the flavor of coffee combines best with the following flavors:
- cereals and sugars: toast, rye, black rice
- nuts and seeds: roasted peanuts, popcorn, and roasted hazelnuts
- condiments and sauces: soy sauce, kecap manis (a thick, sweet Indonesian soy sauce), and balsamic vinegar
In terms of baking, one could easily use rye flour, black rice flour, peanuts, or hazelnuts. Looking a bit further out on the food pairing tree, some other flavors that might work specifically for baking include mango, strawberries, cranberry, cardamom, cinnamon, vanilla, buttermilk, cheddar, honey, tomato, olive oil, American bourbon whiskey, and Sauternes.
it is debatable whether salty is a flavor, I would say it isn't, but there is a practice of adding salt to coffee. There is a whole article about what happens to the taste of coffee when salt is added at the wonderful khymos.org blog, complete with user tests http://blog.khymos.org/2010/03/21/a-pinch-of-salt-for-your-coffee-sir/