Melt butter in a saucepan over medium heat
Add flour and whisk constantly for 1–2 minutes until lightly golden
Slowly whisk in beef broth a little at a time, whisking to prevent lumps
Add milk and continue whisking until smooth
Stir in onion powder, garlic powder, and black pepper
Simmer gently for 5–7 minutes, stirring often, until thickened
Season with salt to taste
Stir in bouillon powder or heavy cream if using
Remove from heat once smooth and pourable