For the Crust: Preheat oven to 350 degrees F. Using a food processor, roughly grind the pecans, graham crackers and spices. Add the melted butter and pulse to mix completely. Press into either a 9” or 10” pie pan, pressing crumbs down firmly using the bottom of a 1 cup measure. Bake for about 14 minutes, or until lightly browned. Set aside to cool completely.
Whip the cream to medium firm peaks, set aside in refrigerator.
For the Swiss meringue: Gently hand whisk the egg whites and 1/4 cup sugar in a small metal bowl set snugly over a pot of simmering water. When sugar is completely dissolved and mixture tops 140 degrees F, about 3 minutes, remove from heat. Using a hand mixer, beat 2 minutes, till mixture starts to thicken. Add spices and continue beating until thickened and cooled. Set aside.
For the Custard:
Whisk gelatin with sherry, rum and water in a small bowl.
To make the custard, whisk together sugar and egg yolks in a small wide metal bowl. Bring milk and salt to a boil in a 2 quart saucepan, then slowly whisk into yolks. Pour mixture back into pan and cook on medium-low heat, stirring constantly with a heat proof spatula or wooden spoon, till it has thickened somewhat and you can run your finger and make a track through the mixture across your spatula. Do not let custard boil or start to curdle. This should only take 3-4 minutes.
Remove from heat and stir in gelatin till completely melted. Pour through a sieve into a clean bowl and cool over an ice bath, whisking occasionally, till mixture starts to cool and set up. You can place the whole setup in the refrigerator to speed things up.
When ready, fold whites, rum and vanilla into custard. Fold in whipped cream. Pour into shell and sprinkle with a bit of mace. Chill until set, at least 3 hours. Serve topped with additional sweetened whipped cream if desired.