Pat chicken pieces thoroughly dry with paper towels to ensure optimal searing.
Season chicken cubes evenly with salt and black pepper.
Heat vegetable oil and 1 tablespoon of butter in a large heavy-bottomed skillet or wok over medium-high heat until the butter foam subsides.
Place chicken in the skillet in a single layer; sear undisturbed for 3 minutes to develop a golden-brown crust.
Stir the chicken and continue cooking for 2 to 3 minutes until the internal temperature reaches 165°F (74°C).
Reduce heat to medium and add the remaining 1 tablespoon of butter, minced garlic, and ground ginger; sauté for 45 seconds until aromatic.
Deglaze the pan with soy sauce and lemon juice, tossing the chicken constantly for 1 minute until the sauce reduces to a light glaze.
Remove from heat and transfer to a serving platter.
Garnish with toasted sesame seeds and sliced green onions before serving.