PASTRY RING:

1/2 stick (1/4 c.) unsalted butter, cut into pieces
1/8 tsp. salt
1/2 c. all-purpose flour
3 lg. eggs
2 tbsp. sliced almonds

GANACHE FILLING:

1 1/2 c. heavy cream
The zest of 2 navel oranges, removed with a vegetable peeler
8 oz. fine-quality semi-sweet chocolate, chopped fine
Confectioners' sugar for dusting the cake

Make the pastry ring: Lightly butter a baking sheet and using an 8-inch round cake pan as a guide, mark an 8-inch circle in a butter on the sheet.

In a heavy saucepan, bring to a boil 1/2 cup water with the butter and the salt over high heat. Reduce heat to moderate, add the flour all at once, and heat the mixture with a wooden spoon until it leaves the side of the pan and forms a ball. Transfer the mixture to a bowl and with an electric mixer beat in 2 of the eggs, one at a time, beating well after each addition.

In another bowl, beat the remaining egg lightly and add to the batter 1 to 2 tablespoons of it, or enough to make the batter stiff enough to just fall from a spoon. Reserve the remaining beaten egg. Spoon the batter into a large pastry bag fitted with a 5/8 inch tip and pipe it into an 8-inch ring on the baking sheet, piping just inside the circle. Pipe another ring just inside the first, touching it, and pipe a third ring on top of the crack between the first 2 rings.

Brush the batter with the reserved beaten egg and mark it decoratively with the tines of a fork dipped in water. Sprinkle the almonds over the ring and bake the pastry ring in the lower third of a preheated 400 degree oven for 35 minutes, or until it is puffed and golden brown. (The cracks that form should also be golden brown.) Transfer the pastry ring to a rack and let it cool.

Halve the pastry horizontally with a serrated knife and scrape out any uncooked dough. The pastry may be made 1 day ahead and kept in an airtight container.

Make the ganacha filling: In a small saucepan, scald the cream with the zest, remove the pan from the heat, and let the mixture stand, covered, for 20 minutes. Strain the mixture through a fine sieve into a bowl, pressing hard on the zest, and return the cream to the pan, cleaned.

Put the chocolate in a heat-proof metal bowl. Bring the cream to a boil, pour it over the chocolate, and whisk the mixture until it is smooth. Let the mixture cool to room temperature, stirring occasionally, and chill it, stirring occasionally, for 30 minutes, or until it is thickened and quite cool but not set. With an electric mixer, beat the ganadre until it lightens in color and holds very soft peaks, but do not over beat it or it will become granular.