1. Make tart shells: Process flour, cocoa, sugar, and fleur de sel in a food processor until combined. Add butter; pulse until mixture resembles coarse meal. With processor running, add eggs; process just until dough comes together.

2. Turn out dough onto a clean work surface; pat together. Wrap in plastic wrap. Refrigerate until firm, about 30 minutes.

3. On a lightly floured work surface, roll out dough to 1/8 inch thick. Using a 3-inch round cookie cutter, cut 10 rounds from dough. Transfer remaining dough to a flour-dusted baking sheet; refrigerate.

4. Fit dough rounds into ten round tartlet molds (each 2 1/4 inches in diameter). Trim edges of dough flush with top edges of molds. (Refrigerate scraps.) Refrigerate shells until cold, 30 minutes.

5. Preheat oven to 350 degrees. Prick bottoms of shells all over with a fork. Bake until firm, about 12 minutes. Let cool completely in molds on a wire rack; unmold.

6. Working in batches of ten and using remaining dough (reroll scraps), repeat steps 3, 4, and 5 to make 40 shells total.

7. Make caramel filling: Heat sugar and 1/2 cup water in a small saucepan over medium-high heat, stirring occasionally, gently, until sugar has dissolved. Continue to cook, without stirring, until syrup comes to a boil, occasionally washing down sides of pan with a wet pastry brush to prevent crystals from forming. Let boil, swirling pan occasionally, until syrup is dark amber. Remove from heat.

8. Carefully stir in cream and port (caramel will steam and spatter). Add butter and chocolate; stir until melted and mixture is smooth. Let cool until slightly thickened but still pourable, about 20 minutes.

9. Cover bottoms of tart shells with almonds (about 1 teaspoon per shell). Spoon caramel filling into shells, filling each almost to the top. Sprinkle with almonds and fleur de sel. Refrigerate until ready to serve, up to 3 hours.