Bialys

In large bowl, dissolve sugar in warm water. Sprinkle yeast over top; let stand until frothy, about 10 minutes. Stir in whole wheat flour and salt. Gradually add bread flour, mixing with wooden spoon until very shaggy dough forms. Knead in mixer with dough hook until very smooth and elastic, about 12 minutes, or by hand for 15 minutes. Place in greased bowl, turning to grease all over. Cover with plastic wrap; let rise in warm draft-free place until doubled in bulk, about 2 hours.

Punch down dough in centre and pull up on sides, pressing sides in. Turn dough and cover; let rise until doubled in bulk, about 1-1/2 hours.

Punch down dough and divide in half. Form each into ball; cover and let rest for 15 minutes. Shape each into 10-inch (25 cm) long rope; cut ropes into 5 pieces. Stretch each piece into ball, pinching ends under; flatten to about 3 inches (8 cm) in diameter. Place on floured work surface and cover with damp cloth. Let rise until doubled in bulk, about 45 minutes.

In bowl, mix together onion, bread crumbs, poppy seeds and oil; set aside.

Press well into centre of each bun. Stretch well to 2 inches (5 cm) in diameter and 1/4-inch (5 mm) thick on bottom, being careful not to deflate dough around well. Spoon heaping teaspoonful (5 mL) of the onion mixture into each well, pressing to adhere. Cover and let rise for 30 minutes.

Heat bread or pizza stone or baking sheet on centre rack of 450°F (230°C) oven. With floured spatula, carefully slide half the bialys, 1 at a time, onto heated stone. Spray inside of oven with 1/3 cup (75 mL) water, avoiding light bulbs and closing door quickly to seal in steam. Bake until golden brown, 13 to 15 minutes. Transfer to rack and let cool. Repeat with remaining bialys. Serve warm or at room temperature. (Make-ahead: Store in airtight container for up to 1 day or freeze for up to 2 weeks.)