Turn them into soup:
Depending on the type of pot you’re using, the onions may get more brown or stay golden; my enameled cast–iron won’t get them a deep brown.
Only when they’re the deepest gold/brown, add 2 tablespoons butter, stirring until melted.
Stir in 1 tablespoon of the flour, then 1/4 cup of the broth. Stir constantly to allow the flour to mix in. Add the remaining flour and cook, stirring, for another 2 minutes to cook off the flour-y taste and again to incorporate it. Add another 1/4 cup of the broth and stir until it’s all a thick base.
Add the remaining broth about a cup at a time, stirring to mix after each addition.
Add the white wine, stir, return to a boil, and reduce to a simmer.
Add the pepper, taste, and adjust.
Simmer 45 minutes to develop flavor and texture. Before serving, adjust salt and pepper if necessary.