Separate the scallions into white parts and green parts. Pat the cubed chicken thighs dry and season evenly with kosher salt and pepper; set aside.

Heat 2 tablespoons olive oil in a large skillet over medium heat until the oil shimmers.

Add the seasoned chicken to the skillet in a single layer. Sauté, stirring occasionally, about 10 minutes, until the chicken starts to brown.

Add the 3 cloves minced garlic and the white parts of the scallions. Sauté, stirring, about 5 minutes, until the scallion whites soften and the garlic is fragrant. Reduce the heat if the garlic starts to brown too quickly.

Add 1/4 cup hoisin sauce, 1/4 cup chicken stock, and 2 tablespoons low-sodium soy sauce to the skillet. Stir to combine.

Add 1/4 cup dried Thai bird eye chilies whole, being careful not to break them. Simmer, stirring occasionally, until the sauce thickens and coats the chicken.

Stir in 2 cups lightly steamed broccoli and 3/4 cup toasted cashews. Cook just until the broccoli is heated through and everything is coated in the sauce.

Sprinkle the reserved scallion greens over the dish and serve immediately over prepared white or brown rice.