Mug Cookie Recipe with Peanut Butter

Ingredients

• 1 tablespoon butter, softened
• 3 tablespoons creamy peanut butter
• 3 tablespoons sugar
• 1 large egg yolk
• 1/4 cup all-purpose flour
• 3 tablespoons 2% milk
• 1/8 teaspoon vanilla extract
• 1 tablespoon chopped unsalted peanuts