Melt the butter in a large saucepan over medium heat.
Add sliced onions and cook, stirring frequently until onions are soft and translucent.
Keep the heat low to avoid browning the onions.
Sprinkle flour over the onions, stirring continuously to blend.
This step forms a base for the soup's consistency that you'll love!
Gradually add the beef broth and bouillon cubes.
Stir well and bring the mixture to a gentle simmer while ensuring all flour lumps are dissolved.
Reduce the heat to low and stir in the heavy cream.
You should avoid boiling the cream to prevent it from curdling.
Add the cheddar cheese, stirring constantly until fully melted.
Taste the soup and adjust the seasoning with salt and pepper if needed.