Trim the onion tops and remove their skins
Cut lengthwise halfway through each onion
Boil the onions for 10 minutes until softened
Rinse briefly in cold water
Carefully separate the layers without tearing them
Mix all the filling ingredients thoroughly in a large bowl
Place a portion of the mixture onto each onion layer and roll it tightly
Arrange the stuffed onions snugly in a pot or pan to keep them secure
Melt butter in a saucepan and let it brown slightly
Add the chicken bouillon, tomato paste, and 2 cups of water, mix well
Pour enough sauce over the stuffed onions to almost fully cover them
Place a sheet of parchment paper over the onions, cover the pot, and simmer on low heat for 35–45 minutes
Broil the onions on high for a few minutes to caramelize the tops, watching closely to prevent burning
