Bring a medium [large] sauce pot of water to a boil. Add the rice noodles and cook until just tender, 8 to 10 minutes. Drain and rinse with cold water, then return to the pot and toss with 1 to 2 teaspoons oil to prevent sticking. While the water is heating and the noodles are cooking, prepare the vegetables and your protein.

• Peel and coarsely chop enough onion to measure 1 cup [2 cups].
• Trim the root ends from the scallions; thinly slice the scallions on the diagonal, keeping the white and green parts separate. Set aside the white parts for the stir-fry and the green parts for garnish. 
• Cut away the cores from the tomatoes; coarsely chop the tomatoes.

• Ground meat: Cut a small corner from the ground meat packaging and drain off any excess liquid. Transfer to a plate; pat dry with a paper towel.
• Shrimp: Rinse and drain the shrimp. Pat dry on a paper-towel-lined plate. 
• Tofu: Pat the tofu dry with paper towels; cut into ½-inch cubes. 
• Plant-based chicken: Pat the plant-based chicken dry with a paper towel.

In a wok or large frying pan over medium-high heat, warm 1 to 2 teaspoons oil until hot but not smoking. Add the onion, season with salt and pepper, and cook, stirring occasionally, until starting to soften, 2 to 3 minutes. 

Add your protein, season with salt and pepper, and cook, stirring and breaking up the ground meat if using, until the protein is lightly browned but not yet cooked through, 1 to 2 minutes.

Stir in the Burmese spice blend and white parts of the scallions and cook until fragrant, 1 to 2 minutes. Add the tomatoes, stir-fry blend, and ¼ cup [½ cup] water and bring to a boil, then reduce to a simmer. Cook, stirring occasionally, until the vegetables are tender and your protein is cooked through, 1 to 2 minutes for regular shrimp; 2 to 3 minutes for jumbo shrimp; and 3 to 4 minutes for ground meat, tofu, or plant-based chicken. Remove from the heat. While your protein and vegetables are cooking, prepare the bok choy.

• Trim the root ends from the bok choy; cut the bok choy in half lengthwise, then crosswise into ½-inch-wide pieces.

In a medium frying pan over medium-high heat, warm 1 to 2 teaspoons oil until hot but not smoking. Add the bok choy, season with salt and pepper, and cook, stirring occasionally, until crisp-tender, 2 to 3 minutes. Remove from the heat. 

To the pan with your protein and vegetables, add the bok choy and rice noodles and toss to combine. Season to taste with salt and pepper.

Transfer the Shan noodles to individual bowls, garnish with the green parts of the scallions, and serve.