With the rack in the middle position, preheat the oven to 350°F (180°C). Butter two 6-cup (1.5 litre), 10 x 4-inch (25 x 10 cm) loaf pans and line each with a sheet of parchment paper, letting it hang over two sides.
In a bowl, combine the bananas and the sour cream. Set aside.
In another bowl, combine the flour, baking soda and salt. Set aside.
In a third bowl, beat the eggs, brown sugar and vanilla with an electric mixer until the mixture triples in volume. Add the oil in a thin stream. Stir in the dry ingredients, alternating with the mashed bananas. With a spatula, stir in the chocolate. Spread the batter into the pans.
Place the banana halves on a plate. Sprinkle with the lemon juice and sugar. Place the banana halves on top of the batter, pushing them in lightly.
Bake for 45 to 50 minutes or until a toothpick inserted in the centre of the loaf comes out clean. Let cool completely on a wire rack.
If you plan on garnishing the loaf with the banana halves, it is best eaten the same day and will not freeze well.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.