Step 1

Combine shallot, crabmeat, mascarpone, and chives in a medium bowl; season with salt. Gently fold to combine. Set aside.

Step 2

Pour oil into a large saucepan fitted with a deep-fry thermometer to a depth of 6". Heat oil over medium-high heat until thermometer registers 375°F.

Step 3

Meanwhile, whisk flour, cornstarch, baking powder, and 1/2 teaspoons salt in a large bowl. Gradually whisk in beer, just to blend (batter will be thick).

Step 4

Working in batches of about 4 and returning oil to 375°F between batches, measure 1 heaping tablespoon crab mixture, roll into a ball, and drop into batter. Using a fork, toss to coat and lift from batter, letting excess drip back into bowl. Carefully lower beignets into oil. Fry, turning occasionally, until crisp and deep golden brown, about 4 minutes. Transfer to a paper towel-lined plate and season with salt.

Step 5

DO AHEAD: Crab mixture can be made 4 hours ahead. Cover and chill.