This is the version that actually cuts into squares. The crust bakes, the filling cooks on the stovetop, and the whole pan sets in the refrigerator rather than the freezer (King Arthur Baking).

One caveat worth stating plainly: King Arthur's published method confirms the crust and filling technique step by step, but the material reviewed here gives timing and yield, not exact cup measurements for the crumbs, butter, sugar, cream, or lime juice. Keep the original recipe card open alongside this guide for the actual ingredient list. What's below is the confirmed sequence and schedule, useful for understanding how a stovetop filling differs from a baked custard, but not a stand-in for the full ingredient list.

You'll need an 8-inch square pan, parchment for a sling, a saucepan, and roughly 7 hours total, most of it hands-off chilling. The listed total is 6 hours 45 minutes (King Arthur Baking).

1. Preheat the oven to 350°F with a rack in the center, and line the pan with a parchment sling so the bars lift out cleanly later (King Arthur Baking).
2. Press the graham cracker crust into the pan and bake for 10 to 15 minutes, until it darkens slightly. Cool on a rack for 10 minutes before adding the filling (King Arthur Baking).
3. Bring the filling to a boil, then reduce the heat slightly and hold a gentle boil for 5 minutes, stirring constantly. It won't thicken the way a custard does; it stays almost as fluid as plain cream (King Arthur Baking).
4. Pour the filling over the slightly cooled crust and refrigerate uncovered for at least 6 hours, or overnight, until set (King Arthur Baking).

Stir the filling occasionally while it cooks. That's what keeps a skin from forming on top before you pour it (King Arthur Baking).

Treat the steps below as a transcription of Ina Garten Cooks' published method, not a kitchen-tested walkthrough. The source contains one unresolved contradiction, flagged further down, that this guide hasn't reconciled.

The filling uses raw egg yolks, and the recipe's own author notes a small salmonella risk from that. Two alternatives are offered: substitute pasteurized eggs, or bake the crust at 350°F for 8 to 10 minutes and cool it completely before filling (Ina Garten Cooks). Settle that question before shopping, since it changes what goes in the cart.

One batch makes a 9-inch pie or four individual mini pies. For the smaller format, divide the crust and filling evenly across mini pans instead of one large one (Ina Garten Cooks).

Ingredients:

• 1½ cups (150g) graham cracker crumbs, from about 12 full sheets (Ina Garten Cooks)
• ¼ cup (50g) granulated sugar (Ina Garten Cooks)
• Melted butter, enough to moisten the crumbs so they hold together when pressed; the material reviewed here doesn't give an exact amount, so check the source directly before shopping
• One 14-ounce (396g) can sweetened condensed milk (Ina Garten Cooks)
• ½ cup (120ml) fresh key lime juice, about 12 to 15 key limes or 4 regular limes (Ina Garten Cooks)
• 4 large egg yolks, raw in the original method, with pasteurized eggs as a substitute per the note above (Ina Garten Cooks)
• 1 cup (240ml) heavy cream, very cold (Ina Garten Cooks)
• 2 tablespoons (15g) confectioners' sugar (Ina Garten Cooks)
• ½ teaspoon pure vanilla extract (Ina Garten Cooks)

No key limes on hand? Regular limes work, though they're less tart; use 6 tablespoons of regular lime juice plus 2 tablespoons of lemon juice to approximate key lime's acidity (Ina Garten Cooks). Gluten-free graham crackers work too, since the rest of the ingredients are naturally gluten-free (Ina Garten Cooks).

Here's the contradiction worth knowing before you start whipping cream: the recipe's ingredient list describes whipping the cream to stiff peaks, while its numbered method says to beat it on medium-high until soft peaks form, about 2 to 3 minutes (Ina Garten Cooks). The source doesn't reconcile the two, and this guide won't guess on your behalf. Use your own judgment on the endpoint, or check the source directly, since the two instructions aren't interchangeable.

Steps:

1. Mix the graham cracker crumbs, sugar, and melted butter, then press into the pie pan or mini pans. Freeze, uncovered and unbaked, for at least 15 minutes while you make the filling; this keeps the crust from going soggy once the filling goes in (Ina Garten Cooks).
2. Whisk the sweetened condensed milk, fresh key lime juice, and egg yolks (pasteurized, if substituting) together until thickened (Ina Garten Cooks).
3. Whip the cold heavy cream with the confectioners' sugar, using the endpoint you settled on above, then fold into the lime mixture (Ina Garten Cooks).
4. Pour the filling into the frozen crust and freeze, uncovered, for at least 6 hours or overnight, until the filling is completely firm (Ina Garten Cooks).

The recipe lists 30 minutes of prep and about 6 hours of freezing elsewhere in the same source, but its stated total time field runs to 8 hours (Ina Garten Cooks). Plan around the longer figure rather than the shorter one.

Chilled bars are done when the center no longer jiggles, generally after the minimum 6-hour refrigeration (King Arthur Baking). For clean squares, soak a chef's knife in hot water, dry it, and slice (King Arthur Baking). Store covered in the fridge up to a week, or freeze for longer, and serve chilled rather than at room temperature (King Arthur Baking).

The frozen pie is done when the filling is completely firm to the touch, after its own minimum 6-hour freeze (Ina Garten Cooks). It produces wedges, not squares, so cut it accordingly. The source lists two thaw windows: 5 to 10 minutes at room temperature, or 30 minutes in the refrigerator (Ina Garten Cooks). For longer storage, wrap tightly in plastic and foil and freeze for up to 2 months (Ina Garten Cooks).

The bar recipe contains no eggs at all. The pie's cited method uses uncooked yolks, with pasteurized eggs or a briefly baked crust offered as alternatives. That's the real fork between these two desserts, not the crust, which is graham cracker in both.

Make the bars if you want an egg-free dessert that cuts into clean squares without any qualifiers. Make the pie if the frozen, mousse-like texture is the actual goal and you've already decided how to handle the egg question.

Neither cited source turns the frozen filling into square-cut bars. Anyone set on that exact shape is better off making the chilled bars rather than trying to bend the pie into a format it was never built for.