Prepare the chicken livers: Wash the chicken livers with cold water and dry them with paper towels. Cut off any stringy or discolored pieces.
Cook the onions and garlic: Heat the olive oil in a big pan over medium heat. Add the chopped onion and cook until it's soft, about 5-7 minutes. Add the garlic and cook for another minute.
Cook the chicken livers: Put the chicken livers in the pan. Cook them for about 3-4 minutes on each side, until they're brown outside but still a little pink inside. If your pan is small, cook them in batches.
Add broth and herbs: Pour in the chicken broth, then add the sage and rosemary. Stir it all together. Let it cook gently for about 2-3 minutes, so the flavors mix.
Blend it all up: Carefully put everything from the pan into a blender. Blend until it's very smooth. If it's too thick, add a bit more chicken broth, one spoonful at a time, until it's just right. Add salt and pepper to your liking.
Get the bread ready: While the liver mix cools, heat your oven to 350°F (175°C). Put the baguette slices on a baking sheet. You can spread a little butter on each slice if you want.
Toast the bread: Bake the bread for 8-10 minutes, until it's golden brown and crispy. Watch it closely so it doesn't burn.
Put it together: Let the toasts cool a bit, then spread a good amount of the chicken liver spread on each one.
Serve right away.