To make the panna cotta: combine the heavy cream, half & half, vanilla bean paste and espresso powder in a medium saucepan over low heat and bring to a gentle simmer.
In a separate bowl, whisk together the egg yolks and both sugars until pale in color. In another small bowl, pour the packet of gelatin over 1/4 cup cold water and allow to sit.
While whisking the eggs, pour some of the warm heavy cream mixture to bring the eggs up to a working temperature. Continue to whisk more of the warm cream into the eggs until the sugar is dissolved. While whisking, whisk the egg mixture back into the heavy cream on the stove. Cook over medium heat while whisking constantly until the mixture has just thickened slightly.
Remove from the heat and strain through a fine mesh strainer into a large measuring cup. Whisk in the bloomed gelatin until smooth. Pour into individual cups or ramekins (mine were 7oz cups) leaving a little room at the top for the ganache. Chill for 4 hours or overnight.
To make the ganache: add the chocolate and heavy cream to a small saucepan over medium-low heat. Whisk until the chocolate is melted and warm. Remove from the heat and whisk in the butter, vanilla and salt. Allow to cool slightly. Transfer to a piping bag or a heavy duty ziplock bag and cut a small hole in the tip or corner. Top each panna cotta with a layer of ganache and return to the fridge for 10 minutes to set.
To make the mascarpone whipped cream: In a medium mixing bowl, whisk the cream vigorously until slightly thickened. Add the mascarpone, powdered sugar and vanilla and whisk until soft peaks form. Top the panna cottas with whipped cream and serve.