Prepare the pie crust: In a bowl, combine the flour, lard, butter and salt. Mix lightly with your fingers until the mixture forms pea-sized pieces. Using a fork, stir in the ice water, a little at a time, until a dough forms, and then knead lightly until it comes together in a ball. Wrap in plastic wrap and refrigerate at least 1 hour or overnight.
On a lightly floured work surface, roll out the dough into a round about 12-inches in diameter and 1/4 inch thick. Drape the round over the rolling pin and transfer to a 9 inch or 10 inch glass or ceramic pie plate. Ease the pastry into the pie plate, pressing it gently against the bottom and sides. Trim the edges, leaving a generous 1/2 inch overhang. Fold the overhang under, then crimp the edges. Cover and chill for 30 to 60 minutes.
Preheat the oven to 350 degrees F. Prick the bottom and sides of the pastry with a fork. Line the pastry with parchment paper or waxed paper and fill with pie weights or dried beans. Bake until lightly browned, 20 to 25 minutes. Remove from oven and remove the weights and paper. Transfer the pie shell to a rack and cool completely.
Filling: In a food processor fitted with the metal blade, combine the lime juice, green food coloring, cream cheese and condensed milk. Process until smooth, scraping down the sides of the work bowl often. Add the lime zest and process to mix thoroughly. Pour into the pie shell and place in the refrigerator.
In a bowl, using a whisk, beat the crema and powdered sugar until soft peaks form. Using a rubber spatula, spread the mixture over the top of the pie, creating peaks evenly over the surface. Garnish with the lime slices. Cover and chill for 4 to 6 hours or overnight before serving.
c.1997, M.S. Milliken & S. Feniger, all rights reserved