Heat butter and olive oil in a large skillet over medium heat.
When hot, add onions. Season lightly with salt and pepper, then cook until translucent and starting to brown (stirring frequently).
Stir in shallots, then cook until onions and shallots are golden to medium-brown (stirring occasionally).
Mix in garlic, then cook just until fragrant, about 30 seconds (stirring constantly).
Sprinkle flour over onion mixture, then stir to coat. Continue cooking for two minutes, or until flour starts to change color (stirring constantly).
Slowly add broth, while whisking vigorously, until fully incorporated. Continue cooking, stirring frequently, until gravy has thickened, about 5 to 10 minutes.
Season to taste with salt and pepper, then serve immediately. Enjoy!
Notes
Recipe makes about 3 cups. One serving is considered ¼ cup, so it will feed about 12 people. If you're serving a crowd, you may want to double the recipe, since some people will inevitably eat more than that.I used yellow onions for this recipe, however red and white onions will also work. Just keep in mind that red onions will affect the color of the gravy. You may also use all onions, skipping the shallots and / or garlic, if you prefer.Check out the info before this recipe card for variations and lots of helpful tips + tricks!