Loosen the cold rice with your hands to separate any clumps.
Heat a large wok or skillet over medium heat. Add bacon and cook until crisp, 6–8 minutes.
Scoop bacon to a bowl. Leave about 1 tablespoon drippings in the pan; discard the rest.
Melt butter in the pan. Pour in beaten eggs and softly scramble. Transfer to the bowl.
Add neutral oil if needed. Sauté onion until translucent, about 2 minutes. Stir in garlic for 30 seconds.
Add peas and carrots. Cook, stirring, until heated through and bright.
Add rice. Press into the pan to sear 1 minute, then stir-fry until hot and steamy.
Pour in soy sauce, oyster sauce, and sesame oil. Add pepper. Toss to coat evenly.
Return bacon and eggs. Fold in scallions. Taste and season with salt if needed. Serve hot.