Cut white portion of each green onion in half lengthwise; combine with green portions. Divide onion pieces into 4 even piles. Set aside.
Combine flour, sugar, and salt in a medium bowl. Add ice water, stirring with a whisk until almost smooth.
Heat a large nonstick skillet over medium-high heat. Add 1 Tbs oil to pan, swirl to coat. arrange 2 onion piles, about 4" apart, keeping onion pieces parallel. Spoon a scant 0.25 C batter over each onion pile, spreading gently into a circle that covers onions. Cook 3 minutes on each side or until crisp and golden.