Cappuccino chocolate chip muffins recipe

Ingredients

• 6 Tablespoons butter, softened
• 2/3 cup sugar
• 1/4 cup milk
• 1-1/2 teaspoons baking powder
• 1/2 teaspoon salt
• 1-3/4 cups unsifted all-purpose flour
• 1 teaspoon vanilla extract
• 1 large egg
• 2 Tablespoons instant coffee dissolved in 2 Tablespoons boiling water
• 1 Tablespoon coffee-flavored liquor (optional)
• 3/4 cup chocolate chips