Heat the oven to 325°F. Toss the sliced almonds, shredded coconut, allulose, melted butter, and salt together, then spread the mixture on a parchment-lined baking sheet.
Bake the crunch for 8 to 10 minutes, stirring once, until lightly toasted. Cool completely, then divide most of it among 8 small dessert cups.
Warm 1/4 cup of the heavy cream until steaming, then pour it over the chopped chocolate. Let it stand for 2 minutes and stir until smooth, then cool until barely warm.
Beat the remaining 1 1/4 cups heavy cream with the powdered allulose, cocoa powder, vanilla, and salt until soft peaks form. Fold the cooled chocolate mixture into the whipped cream in three additions.
Spoon the mousse over the almond crunch and refrigerate for 1 hour.
Melt the chocolate and coconut oil for the shell until smooth. Spoon a thin layer over each chilled mousse cup, then immediately sprinkle with the reserved almond crunch.
Refrigerate for 10 minutes, just until the chocolate shell is crisp, and serve chilled.