Grease a 9-inch pie dish with butter or shortening.
Melt the 7 tablespoons butter in the microwave in 30-second increments until melted.
Crush 11 graham crackers in a food processor into fine crumbs.
Pour in melted butter while running the processor on low until crumbs look like wet sand.
Press crumbs firmly into the bottom and sides of the pie dish. Freeze for 15-20 minutes.
Make the filling
In a large bowl, whisk together 14 oz sweetened condensed milk and 6 oz can pink lemonade concentrate concentrate until smooth.
Add 3 small drops red food coloring (if using) and whisk to combine.
Fold in 8 oz whipped topping until fully mixed.
Fill and freeze
Pour filling into the frozen crust. Cover with plastic wrap and freeze for at least 6 hours or until set.
Top with whipped cream and lemon slices to serve.
Notes
This pie will soften quickly at room temperature, so I recommend keeping it in the freezer after you’ve served the desired number of slices to keep it from getting too soft.
Use a flat-bottom glass or measuring cup to press the crumbs firmly into the pie dish. That will ensure that the crust won’t fall apart when the pie is sliced.