Tiramisu Panna Cotta

Ingredients

• 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, plus more
• 1 Tbsp. vanilla extract
• 2 envelopes unflavored powdered gelatin (about 1 Tbsp. plus 2 tsp.)
• 1⅔ cups whole milk
• 2 Tbsp. instant espresso powder
• ¾ cup plus 2 Tbsp. plus 1 tsp. (179 g) sugar, divided
• 2 Tbsp. Dutch-process cocoa powder, plus more for dusting
• 8 oz. mascarpone
• 4 cups heavy cream, divided
• 3 Tbsp. dark rum
• Chopped chocolate-covered coffee beans (for topping; optional)