Gluten-Free Key Lime Bars
By America's Test KitchenPublished on July 6, 2016
Time
1½ hours, plus 2½ hours cooling
Yield
Makes 16 bars
Ingredients
Crust
6 ounces (170 grams/1 ⅓ cups) America's Test Kitchen All-Purpose Gluten-Free Flour Blend 2 ⅓ ounces (66 grams/⅓ cup) sugar ¼ teaspoon salt ¼ teaspoon xanthan gum 8 tablespoons unsalted butter, cut into ½-inch pieces and softenedFilling
2 ounces (57 grams) cream cheese, softened1 tablespoon grated lime zest plus ½ cup juice (4 limes)Pinch salt 1 (14 ounces/397 grams) can sweetened condensed milk 1 large egg yolk ¾ cup sweetened shredded coconut, toasted (optional)Before You Begin
Letting the bars cool for a full 2 hours and then refrigerating them for an additional 2 hours were key to ensuring the custard topping set up. You can use either Key limes or regular limes here; Key limes have a delicate flavor, while regular limes have a stronger, more tart flavor. In order to yield 1/2 cup of juice, you’ll need about 20 Key limes or 4 regular limes; do not substitute bottled lime juice. Be sure to zest the limes before juicing them. This recipe uses our America's Test Kitchen All-Purpose Gluten-Free Flour Blend.
Instructions
- Adjust oven rack to middle position and heat oven to 350 degrees. Make foil sling for 8-inch square baking pan by folding 2 long sheets of aluminum foil so each is 8 inches wide. Lay sheets of foil in pan perpendicular to each other, with extra foil hanging over edges. Push foil into corners and up sides of pan, smoothing foil flush to pan; spray with vegetable oil spray.
- Using stand mixer fitted with paddle, mix flour blend, sugar, salt, and xanthan gum on low speed until combined. Add butter, 1 piece at a time, and continue to mix until dough forms and pulls away from sides of bowl, 2 to 3 minutes. (Add 1 to 2 tablespoons of water as needed if dough appears dry.)
- Transfer mixture to prepared pan and press firmly into even layer using bottom of measuring cup. Bake crust until fragrant and beginning to brown, 25 to 30 minutes, rotating pan halfway through baking. Let crust cool for about 30 minutes.
- Stir cream cheese, lime zest, and salt together in bowl until well combined and no lumps remain. Whisk in condensed milk until well combined. Whisk in lime juice and egg yolk until very smooth. Pour filling evenly over cooled crust. Bake until bars are set and edges begin to pull away slightly from sides of pan, 15 to 20 minutes, rotating pan halfway through baking.
- Let bars cool completely in pan, about 2 hours. Cover with foil and refrigerate bars until thoroughly chilled, about 2 hours. Using foil sling, remove bars from pan. Sprinkle with toasted coconut, if using. Cut into squares and serve. (Bars can be refrigerated for up to 2 days; crust will soften.)
for the crust
for the filling
Time
1½ hours, plus 2½ hours coolingYield
Makes 16 barsIngredients
Crust
Filling
Ingredients
Crust
Filling
Ingredients
Crust
Filling
Why This Recipe Works
We wanted to bring all the essence of Key lime pie to a Key lime bar, creating a bar that balanced a tart and creamy topping and a buttery rich base. For the base, we wanted something similar to shortbread: a crisp, buttery crust that could support the topping yet slice neatly and easily. We started with a classic shortbread recipe by mixing pieces of softened butter into our all-purpose gluten-free flour blend, along with sugar and salt, using a stand mixer to ensure a fine crumb. The flavor was exactly what we wanted, but without gluten this base couldn’t support the topping. Adding just 1/4 teaspoon of xanthan gum gave the crust the structure it needed to hold up and slice neatly without crumbling. As for the filling, it also had to be sturdy and sliceable. By adding cream cheese and an egg yolk to the usual sweetened condensed milk and lime juice and zest, we created a rich and firm filling.
Before You Begin
Letting the bars cool for a full 2 hours and then refrigerating them for an additional 2 hours were key to ensuring the custard topping set up. You can use either Key limes or regular limes here; Key limes have a delicate flavor, while regular limes have a stronger, more tart flavor. In order to yield 1/2 cup of juice, you’ll need about 20 Key limes or 4 regular limes; do not substitute bottled lime juice. Be sure to zest the limes before juicing them. This recipe uses our America's Test Kitchen All-Purpose Gluten-Free Flour Blend.
Instructions
- Adjust oven rack to middle position and heat oven to 350 degrees. Make foil sling for 8-inch square baking pan by folding 2 long sheets of aluminum foil so each is 8 inches wide. Lay sheets of foil in pan perpendicular to each other, with extra foil hanging over edges. Push foil into corners and up sides of pan, smoothing foil flush to pan; spray with vegetable oil spray.
- Using stand mixer fitted with paddle, mix flour blend, sugar, salt, and xanthan gum on low speed until combined. Add butter, 1 piece at a time, and continue to mix until dough forms and pulls away from sides of bowl, 2 to 3 minutes. (Add 1 to 2 tablespoons of water as needed if dough appears dry.)
- Transfer mixture to prepared pan and press firmly into even layer using bottom of measuring cup. Bake crust until fragrant and beginning to brown, 25 to 30 minutes, rotating pan halfway through baking. Let crust cool for about 30 minutes.
- Stir cream cheese, lime zest, and salt together in bowl until well combined and no lumps remain. Whisk in condensed milk until well combined. Whisk in lime juice and egg yolk until very smooth. Pour filling evenly over cooled crust. Bake until bars are set and edges begin to pull away slightly from sides of pan, 15 to 20 minutes, rotating pan halfway through baking.
- Let bars cool completely in pan, about 2 hours. Cover with foil and refrigerate bars until thoroughly chilled, about 2 hours. Using foil sling, remove bars from pan. Sprinkle with toasted coconut, if using. Cut into squares and serve. (Bars can be refrigerated for up to 2 days; crust will soften.)
for the crust
for the filling
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