Step 3
To make the filling: In a large saute pan over medium heat, melt the butter. Add the yellow onion, garlic, celery, pearl onions, and carrots. Saute, stirring occasionally, until the carrots are just cooked, 8 to 10 minutes. Add the flour and cook, stirring constantly, for about 2 minutes. Add the broth, cognac, salt, and white pepper. Bring to a boil, stirring with a wooden spoon and scraping the bottom and corners of the pan to incorporate the flour. Simmer until thickened, a few minutes. Off the heat, stir in the heavy cream, thyme, chicken, and peas. Taste and adjust seasoning, if necessary. (Note that the broth will taste a little boozy at this point. That's okay - the cognac will cook-off in the oven.) Ladle the filling into 4 large or 6 small oven-safe soup bowls. The filling should come up no more than three-quarters of the way to the top of the bowls. Do not overfill.