To make the tart shells:
Combine the flour, nuts, and sugar in a mixing bowl. Using a fork, cut in the butter to just blend. Stir in the egg yolks, mixing with the fork just until the dough comes together. If necessary, add ice water, a few drops at a time.
Form the dough into a ball and wrap in plastic film. Refrigerate for 1 hour, or until thoroughly chilled.
When ready to roll out, lightly flour a clean, flat work surface.
Preheat the oven to 350°F.
Lightly butter six 4-inch round fluted tart pans with a removable bottom.
Remove the dough from the refrigerator and unwrap it. Place it on the lightly floured surface and, using a rolling pin, roll out to a circle about 1/8 inch thick.
Using a plain or fluted 5-inch round cutter, cut 6 dough circles. Working with one at a time, fit a pastry round into each tart shell, pressing it into the bottom and sides. Work carefully, as the dough is a bit fragile. If it breaks, just push it together with your fingertips. Even the edge of the pastry with the rim of the pan.
Place the tart shells on a baking sheet and bake for about 10 minutes, or until lightly browned. Remove from the oven and place on wire racks to cool until ready to fill.
To make the chocolate filling:
Place the chocolate and grated orange zest in a heatproof mixing bowl. Set aside.
Combine the cream and honey in a medium heavy-bottomed saucepan over medium heat. Heat just until bubbles form around the edge of the pan. Immediately remove from the heat and pour half of the mixture over the chocolate. Let stand for 30 seconds and then whisk to blend. Add the remaining hot cream and again let stand for 30 seconds. Then beat until smooth. Add the butter and beat to blend.
Pour an equal portion of the chocolate mixture into each tart shell, carefully smoothing the top with an offset spatula. Transfer to the refrigerator and let chill for at least 1½ hours or up to 6 hours before serving.
Serve chilled, garnished with candied orange zest or chopped nuts and a dollop of whipped cream, if desired.