1 1/2cupshalf-and-half(or 3/4 cup heavy cream + 3/4 cup whole milk)
1/2cupkey lime juice
In a medium bowl, preferably one with a spout, whisk together the sweetened condensed milk, half-and-half, and key lime juice.
Divide the mixture evenly between popsicle molds, leaving a small amount of room at the top. Sprinkle graham cracker crumbs on top of each pop and gently press into the liquid to help freeze them in place. (Note: Do not submerge the graham crackers completely.)
Top with the popsicle sticks and freeze until solid, at least two hours. To serve, briefly run the molds under warm water to help remove the pops.
Optional: dip the sides of the pops in additional graham cracker crumbs.
Regular limes may be substituted. You can use fresh key limes if they're available, but I used bottled key lime juice.