In a skillet on medium-high heat, fry the onions for 2 minutes in olive oil. Add the peppers and garlic, and then cook for 3 more minutes. Add salt and pepper to taste, turn off the stove and set the mixture aside.
Preheat the oven to 190 °C (375 °F). In a large bowl, combine the Boursin® with the fried vegetables. Fill the shells with the mixture and place them on a baking sheet. Bake for 10 minutes.
Garnish each shell with a leaf of fresh coriander and serve immediately.