Place the potatoes in a medium saucepan and cover with cold water by 1 inch. Bring to a boil over high heat. Once boiling, carefully lower in the eggs with a spoon. Cook the eggs for 10 minutes, then transfer them to a bowl of cold water. Continue cooking the potatoes until fork-tender, about 2 to 4 minutes longer. Drain the potatoes and let them cool slightly. Peel and halve or quarter the eggs.

While the potatoes cook, cut the tofu into 3/4-inch cubes. Heat the oil in a large nonstick skillet over medium-high heat. Add the tofu in one layer and cook, turning occasionally, until lightly golden on several sides, about 7 to 8 minutes.

Bring a second saucepan or deep skillet of water to a boil. Add the green beans and cabbage and cook until bright and just tender, about 2 minutes. Add the bean sprouts for the final 30 seconds. Drain immediately and rinse briefly under cool water to stop the vegetables from overcooking. Shake off excess water.

In a medium bowl, whisk the peanut butter, warm water, kecap manis, lime juice, sambal oelek, and garlic until smooth. Add warm water, 1 tablespoon (15 mL) at a time, until the sauce is pourable but still thick enough to coat a spoon.

Arrange the potatoes, eggs, tofu, blanched vegetables, and cucumber on a large platter or in four bowls. Spoon peanut sauce over the top, or serve it alongside so everyone can add their own. Finish with crispy fried onions, if using, and serve with rice if desired.