In a mixing bowl, whisk together the baking powder, cornstarch, salt, and flour. Gradually whisk in the beer and continue stirring until the batter is smooth and ribbony. Set aside.
Filling
Mix together mascarpone, chocolate chips, and all but 1 Tbsp powdered sugar.
Refrigerate for 10-15 minutes while you prepare the raspberry sauce.
Frying the beignets
Fill a heavy cast-iron skillet ¾ full with peanut oil (about 3 cups) and heat oil to 375 ℉.
Roll ping-pong size balls (about 1 Tbsp) of the mascarpone mixture and use a spoon to drop them onto the top of the beer batter.
Gently roll the balls in the batter to completely coat. If you leave any holes, the mascarpone will leak out. Lift the balls from the batter and let them slide off the spoon into the hot oil. Fry in batches until crisp and deeply golden brown, about 4 minutes. Keep your eye on the temperature and adjust the flame if necessary to keep the temperature at 375 ℉.
When the beignets are done, use a spider strainer to remove them from oil, and place on paper towels to drain.
Prepare a serving dish with a layer of raspberry sauce. Place the beignets onto the sauce. Sprinkle with the remaining powdered sugar. Drizzle some raspberry sauce on the top for garnish.