Heat a large pan over medium heat. When hot, add the oil and when the oil is hot, add the beef. Stir while cooking to break up the ground beef into pieces. Cook until no longer pink, about 5-10 minutes. Add the garlic and ginger and cook until fragrant, one minute more.
Add the bok choy, soy sauce, monk fruit, and rice vinegar and cook, stirring often until the bok choy is softened and there is little liquid left. Adjust seasoning with salt and pepper and stir in the sesame oil off heat.
Whisk the mayonnaise together with the sriracha, season to taste with salt and pepper and a bit of monk fruit, if desired. Thin with water as needed. Drizzle over the beef and bok choy to serve.