Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius).

In a large bowl, combine flour, sugar, and butter until well blended.

Add the egg and vanilla extract and mix until the dough forms.

Stir in pecans and coconut until evenly distributed.

Press the dough into a 9x13 inch baking pan.

In a small saucepan, combine caramels and evaporated milk. Heat over medium heat, stirring constantly, until caramels are melted and smooth.

Pour caramel sauce over the crust.

Sprinkle with marshmallows and chocolate chips (if using).

Bake for 20-25 minutes, or until the crust is golden brown and the marshmallows are puffed up.

Let the cake cool completely before slicing and serving.