You may immediately think of whiskey and coffee liqueur to mix with espresso, but don't limit yourself to these only. Spirits like vodka, tequila, gin and rum make good partners for espresso in both hot toddy-style drinks that you serve in mugs or for cold cocktails in long-stemmed glasses. Have simple syrup -- purchased or homemade by boiling equal parts sugar and water -- on hand as a sweetener if the espresso taste is stronger or more bitter than you prefer.
For a basic espresso martini, mix equal parts cold espresso and Kahlua with two parts vodka and 1/2 part simple syrup. Vary this basic theme by flavoring the drink with liqueurs like raspberry, dark cacao or cream liqueur, using a flavored vodka or adding a shot of another spirit, such as cognac. If you're a fan of the hazelnut liqueur Frangelico, mix it with an equal part of vodka and 3/4 part cold espresso to make a truffle cocktail.
Combine the flavors of a spiced latte with the kick of a margarita by stirring cream, sugar, spices such as cinnamon, vanilla extract and tequila, into hot espresso. Give the drink a pumpkin spice twist by adding pumpkin spice syrup and pumpkin pie spice. Make another hot tequila cocktail, the morning rooster, by stirring one part coffee liqueur and three parts tequila into a cup of freshly brewed espresso and flavor with vanilla extract, heavy cream and a sweetener such as agave nectar.
Combine equal parts simple syrup and freshly squeezed orange juice with two parts of espresso and three parts gin to make an espresso summer. Add slightly crushed ripe blackberries to the ice in a cocktail shaker when mixing the drink, strain, and serve garnished with more blackberries and an orange wedge. Mix the gin and strongly brewed espresso into a small amount of absinthe for a Bronx bomber. For a gin-based, English-style version of Irish coffee, stir London dry gin, triple sec and coffee liqueur into espresso, adding sweetener, if desired.
A.J. Rathbun, author of the cocktail cookbook, "Good Spirits," suggests making chilled island coffee from espresso, dark rum, Kahlua, heavy cream and coffee liqueur. Use equal parts rum and Kahlua, two parts espresso and half a part each of cream and liqueur. Rum is also the basis for paradise found, a cocktail containing butterscotch schnapps along with espresso. For every 6 ounces of coffee, use equal parts schnapps and spiced rum. Serve the drink over ice, garnished with whipped cream.