Bring a large saucepan of water to a low simmer. Add the vinegar.
Crack each egg into a small glass. One at a time, gently and slowly pour each egg into the simmering water, bringing the lip of the glass right down to the water so that the egg slides in. Depending on the size of your pan, you may need to cook them in 2 batches.
Cook for 4 minutes, then use a slotted spoon to lift each egg out (letting excess water drip away). Nestle one egg into the ricotta in each serving bowl.
Season the eggs with salt and pepper, then drizzle with truffle oil and sprinkle with chives. Serve immediately with the toast.
Nutrition information per serving: 550 calories; 290 calories from fat (53 percent of total calories); 32 g fat (15 g saturated; 0 g trans fats); 260 mg cholesterol; 37 g carbohydrate; 7 g fiber; 6 g sugar; 29 g protein; 730 mg sodium
Food Editor J.M. Hirsch is author of the cookbook “High Flavor, Low Labor: Reinventing Weeknight Cooking.”