Cook the bacon in a skillet and remove, reserving 2-3 Tbsp of the grease. Chop the bacon into bits.
Beat the egg yolk, with the 3 Tbsp of sugar and 3 Tbsp vinegar together. Set aside.
Premix the next 3 Tbsp of vinegar and 6 Tbsp of water together and set aside.
Add the flour to the bacon grease in the skillet to make a roux. Stir continuously until the flour takes on a little color.
Add the onions to the roux to cook them, stirring frequently.
Slowly add the water and vinegar mix to the roux, stirring constantly.
Slowly add the egg yolk mixture to roux, stirring constantly.
Add the bacon bits, and stir through.
Put the chopped lettuce into salad bowls and place 3 tablespoons of hot dressing in the center of each. Garnish with the egg slices and cracked black pepper or paprika.