Brew your coffee: Prepare a strong cup of coffee, preferably espresso. Keep it hot.
Prepare the glass: Add the sugar to a heatproof glass or mug. Pour in your chosen spirit (rum, brandy, or whisky).
Optional flambé: If you're feeling adventurous, carefully ignite the spirit in the glass using a long match or lighter. Swirl the glass gently to caramelize the sugar and then let the flames die down. Be cautious when flambéing.
Combine: Pour the hot coffee over the spirit in the glass. Stir gently to dissolve the sugar and combine the flavors.
Garnish: Twist the strip of orange peel over the drink to release its oils, then drop it into the Carajillo. If using, add a splash of Licor 43.
Serve immediately and enjoy the warming embrace of this Spanish classic.