If using fresh broccoli, clean, cut into florets, and steam for 8 minutes or so, checking frequently so it's not too mushy.

Dice the onion

Brown the beef in 1 tbsp butter. DO NOT SALT THE MEAT. Once the beef is mostly cooked through, add the onion. When the onion is translucent, drain the fat if there is a lot. Meanwhile, mince the garlic. Add the garlic to the skillet with the browned beef and onion and continue to cook over medium heat for 1-2 minutes, until the garlic has softened slightly.

Add the broccoli florets (if using frozen, add from frozen here) and continue to sautee over medium heat until the broccoli is no longer frozen. It doesn't need to be completely heated through yet.

Melt 2 tbsp of the butter in a bowl (microwave for about 20 seconds with a paper towel on top) and then add the oyster sauce, soy sauce, brown sugar, and sesame oil. Stir to combine then taste to see if you need additional sugar. Pour into pan.

Continue to cook until the broccoli is hot and the sauce has thickened.

Serve with a pinch of crushed red pepper flakes, if desired.