In a large bowl, whisk together chili sauce, soy sauce, sugar, rice-wine vinegar, tomato paste, sesame oil, and 1 1/4 cups of water.

Set the mixture aside.

Combine shallots, garlic, ginger, and salt in a food processor.

Pulse until a smooth paste forms.

In a separate small bowl, whisk cornstarch with 2 tablespoons of water to create a slurry.

Heat peanut oil in a wok over high heat until it shimmers.

Add the shallot paste to the wok and fry for 30 seconds, or until very fragrant.

Introduce the crabs and one-third of the chili sauce mixture to the wok.

Simmer the mixture for 2 minutes, shaking the wok to coat the crabs with the sauce.

Add the remaining chili sauce to the wok and bring it to a simmer.

Reduce the heat to medium-low, cover the wok, and simmer vigorously for about 8 minutes.

Stir in the cornstarch paste, and cook until the liquid in the wok thickens.

Turn off the heat.

Add the beaten egg yolk and stir thoroughly to combine.

Divide the crabs and sauce among 4 plates.

Garnish with chopped scallions and serve immediately with crab picks and napkins.