Prepare the pressure cooker by filling it with 1 cup of water and placing a raised trivet or rack in the bottom.
In a small bowl, gently mix the egg yolks, maple sugar and salt.
Gently heat the cream: put the cream in a small saucepan over medium heat until steam just begins to rise from its surface (do not boil). Alternately, the cream can be heated in a small bowl or large measuring cup in the microwave, carefully watched in 45 second cooking increments. After removing the cream from the heat, stir in the vanilla extract and espresso powder.
Temper the egg yolks by pouring in 1-2 tablespoons of the warm cream mixture and gently whisking it in until smooth. Slowly pour in the rest of the cream and gently whisk to combine (try not to create too many bubbles).
Pour the mixture into four or six 4 oz. ramekins, and cover each with aluminum foil. Carefully arrange them in the pressure cooker, stacked on top of the trivet in two layers, spaced evenly.
Cover the pressure cooker with the lid, ensuring that the valve is in sealed position. Cook under high pressure for 10 minutes (with Instant Pot, choose ‘Steam’ mode, and leave time adjusted to 10 minutes).
When the cooking time is complete, allow the pot to de-pressurize naturally for at least 10 minutes before opening the lid. Carefully transfer the ramekins to a rack to cool for 30 minutes, then chill in the refrigerator for at least 2 hours. The custard can be prepared to this point up to 3 days ahead of time before serving.
To finish, sprinkle about 1 1/2 teaspoons of maple sugar in an even layer over the top of each custard. Light a butane kitchen torch and carefully pass its flame over the surface, moving continuously, until the sugar bubbles and caramelizes. Serve immediately.