Crust
4 tbsp. pareve margarine
2 cups ground walnuts (from 4 cups walnut halves)
3 tbsp. light brown sugar
Lime Filling
5 large eggs plus 3 yolks
1 1/2 cups sugar
7 limes or 14 key limes
1/2 cup (1 stick) parve margarine
1 drop green food colouring (optional)
Meringue Topping
2/3 cup sugar
1/4 cup water
2 large egg whites
Preheat the oven to 350F. You will need an 8- or 9-inch pie pan.
To make the crust: place the margarine in a medium microwave-safe bowl and heat for 45 seconds, or until melted. Add the walnuts and brown sugar and mix until combined. Place this mixture into the pie pan and press to cover the bottom and about 1 inch up the sides. Place in the oven for 15 minutes. Remove from oven and set aside. Leave the oven on.
To make the lime cream: place the eggs, yolks and sugar in a heatproof bowl and set over a medium saucepan with simmering water (or use a double-boiler). Stir to combine. Juice 4 of the limes or 8 key limes (about 1/2 cup juice) and stir into the egg and sugar mixture. Cook uncovered over simmering water for about 25 minutes, stirring occasionally, until a thick mixture is formed. Be patient and do not stir too much. If the water in the double boiler boils too fast, turn down the heat. Remove the bowl from the heat and whisk in the margarine in small pieces until the cream is smooth. Add the green food colouring, if using, and stir.
Pour the cream into the prepared crust and smooth. Place the pie on a cookie sheet and bake for 20 minutes, or until the outside edges of the cream are set (the inside can remain a little wobbly). Let cool and then place in the refrigerator for at least 2 hours.
To make the meringue topping: in a small heavy saucepan, bring the sugar and water to a boil, stirring to dissolve the sugar. Continue to cook the sugar until it reaches 230ºF (use a candy thermometer to check the temperature). You can dip a pastry brush in water and wipe down the sides of the pot if any sugar crystals appear on the sides.
While the sugar is cooking, in medium bowl, beat the egg whites with an electric mixer on high speed until stiff. When the sugar is ready, turn the mixer speed to low and then slowly pour the cooked sugar into the bowl, down the side of the bowl, not directly onto the wire whisk. When all of the sugar has been poured in, turn the mixer up to medium-high and beat for 1 minute until the meringue is thick and shiny.
Use a silicone spatula to spread the meringue all over the top of the pie. You can use a blow torch to lightly brown the top or place it in a 450-degree oven for a few minutes, watching the entire time, until the top browns.
Storage: Store in the refrigerator for up to five days.