Ooey Gooey Bars

Ingredients:
For the crust layer:

1 ½ cups crushed graham crackers (about 12 crackers)
½ cup sugar
½ cup unsalted butter, melted
For the topping layer:

1 can (14 oz) sweetened condensed milk
1 cup chocolate chips (dark or milk)
1 cup butterscotch chips
1 cup chopped pecans (optional)
1 teaspoon vanilla
For the top layer:

1 cup mini marshmallows (optional)
Instructions: