Start the vegetables: Put a large soup pot or Dutch oven on the stove over medium heat.

Add the olive oil to the pot and let it warm for about 30 seconds.

Add the onion, carrots, and celery to the pot with a big pinch of salt. Cook for 8 minutes, stirring now and then, until the vegetables soften and the onion looks glossy.

Add the garlic and dried oregano to the pot. Stir for 1 minute, just until the garlic smells fragrant.

Add the lentils to the pot. Pour in the vegetable broth and stir well.

Raise the heat to high and bring the soup to a boil.

Lower the heat to maintain a gentle simmer. Partly cover the pot and cook for 25 to 30 minutes, until the lentils are almost tender but still hold their shape.

Add the drained chickpeas to the pot. Simmer for 8 to 10 minutes more, until the lentils are fully tender and the chickpeas are heated through.

Warm the egg and lemon: Ladle 1 cup of the hot broth from the pot into a heatproof measuring cup or bowl.

Crack the eggs into a medium bowl. Whisk until the yolks and whites are fully blended and no streaks remain.

Whisk the lemon juice into the eggs until smooth.

Slowly drizzle about half of the hot broth into the egg-and-lemon bowl while whisking constantly. This warms the eggs gently so they mix into the soup without scrambling.