Step 1Set a baking sheet on the bottom rack (or middle rack, if you prefer) of the oven; heat the oven to 425 degrees.
Step 2Melt the jelly in a small pot over low heat or in a small bowl at 3/4 power in the microwave oven, stirring until smooth. Cool slightly.
Step 3Place the butter and sugar in a mixing bowl. Beat with a mixer at medium speed or with a wooden spoon until thoroughly blended. Add the eggs one at a time, beating until blended after each.
Step 4Warm the pastry shell in the oven for 5 minutes.
Step 5Meanwhile, whisk the cream, half-and-half and vanilla into the jelly until blended, then pour into the butter, beating with a wooden spoon until smooth.
Step 6Remove the shell from the oven and pour the mixture into it. The sieve is not necessary.
Step 7Set the pie on the baking sheet and bake 10 minutes. If on the bottom rack, carefully move the sheet and pie up to the center rack. Place a tent of foil over the pie, shiny side up. Reduce the temperature to 350 degrees and continue baking until the custard tests ready to remove using the knife test: Insert a table knife just off-center; when it comes out with solid bits of custard attached, it's ready--25 to 35 minutes more. Cool, then, if necessary, refrigerate until an hour or so before serving.
Step 8Just before serving, sprinkle a suspicion of mace over the top.