Special equipment: a 6-count popover pan (each cup about a 2/3 cup capacity)
For the popovers: Position a rack in the center of the oven and preheat the oven to 400 degrees F. Spray a 6-count popover pan, six 1 cup ceramic souffle dishes, glass custard cups, or muffin cups with vegetable oil cooking spray.
In a blender, combine the milk, flour, butter, sugar, salt, ginger and eggs and blend until smooth. Scrape down the sides and blend until the batter is very smooth. Divide the batter equally among the prepared dishes, about 1/3 cup each.
Bake the popovers without opening the oven door, until puffed and deep brown, 35 to 40 minutes.
For the salad: While the popovers bake, in a large bowl, combine the orange and lime zest, orange and lime juices, creme fraiche, salt and pepper. Gradually whisk in the oil. Add the crabmeat, radicchio, onions, avocado and mango. Toss until combined.
When the popovers are baked through, remove the popovers from the oven. Twist each out of its dish and cool on a wire rack.
Place the popovers on a platter. Using a serrated knife, remove the tops of the popovers. Using a large spoon, fill each popover with the salad, mounding in the center. Serve immediately.