Brussels Sprouts With Fennel

1 cup walnuts , coarsely chopped 1 lb Brussels sprout , trimmed and halved 1 pint small shallots or 1 pint white pearl onion 2 tablespoons unsalted butter ,[...]

1 small fennel bulb (~1.5 lb.) 16 ounces frozen Brussels sprouts 1 Spanish onion , thinly sliced 1/4 cup olive oil 1/2 teaspoon sugar 1 teaspoon salt 1/2[...]