Preheat your oven to 350°F (175°C).
Grease your 9-inch pie dish lightly with butter or non-stick spray.
In a large mixing bowl, combine the melted unsalted butter, light brown sugar, and granulated sugar. Whisk until smooth and creamy. Add in the large egg and vanilla extract, mixing until fully incorporated.
In another bowl, whisk together the all-purpose flour and a pinch of salt (if using). Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
Gently fold in the semi-sweet chocolate chips, half of the M&M's, mini peanut butter cups, and Rolos.
Spoon the cookie dough into the prepared pie dish, spreading it out evenly. Sprinkle the remaining M&M's on top.
Place the pie dish in the preheated oven and bake for 25-30 minutes, or until the edges are golden and the center is set but still soft.
Once baked, let the cookie pie cool in the dish for about 10 minutes. Slice into wedges and serve warm.
