Preheat the oven to 350 degrees Fahrenheit. Line a cupcake pan with 12 cupcake liners.
Pulse the graham cracker squares in a food processor. Alternatively, you can place the crackers in a gallon-size Ziplock bag and crush them with a rolling pin.
Place the crushed graham cracker crumbs into a medium bowl. Add the sugar and melted butter and mix until combined.
Press 1 tablespoon graham cracker mixture into the bottom of a cupcake liner. Place the cupcake pan into the freezer to help the crust set up while you mix the pie filling.
In a separate bowl, add egg whites, condensed milk, lime juice, lime zest, and yogurt. Using an electric hand mixer, mix well until smooth and creamy.
Fill the cupcakes about ¾ of the way full with the pie filling. Bake for 12-15 minutes and cool completely. Refrigerate until ready to serve!
Top with whipped cream and garnish with a lime slice, if desired. Store in the refrigerator.