Trim the stem ends from the Brussels sprouts, removing any yellowing outer leaves, and split the sprouts in half, lengthwise. (Any unusually large specimens should be quartered.) Place the Brussels sprouts, water, and 1 teaspoon of the salt into a 10-inch straight sided saute pan over medium-high heat. Cover and cook until tender, about 5 minutes. If there is any water left in the pan at this point, continue to cook with the lid off until it evaporates. Remove the sprouts to a medium bowl.
Return the pan to the burner and reduce the heat to medium-low. Add the bacon and cook, stirring frequently, until crisp and brown, 10 minutes. Remove the cooked bacon with a slotted spoon to the bowl with the sprouts. Pour the bacon fat into a heatproof measuring cup and add 1 tablespoon back into the pan. (Reserve the remainder...because bacon fat.)
Add the leeks, pears, and remaining 1/2 teaspoon salt to the pan and saute, stirring frequently, for 2 minutes. Add the Dijon and vinegar, and stir to incorporate. Follow with the heavy cream, black pepper, and nutmeg. Simmer for 1 minute. Break up the blue cheese into smaller bits and add it to the cream mixture, stirring until it melts into the sauce.
Add the sprouts and bacon back to the pan and stir to thoroughly coat. Simmer an additional 2 minutes to "tighten" the sauce and meld the flavors.
Spoon onto a large plate or platter, garnish with the toasted walnuts, and serve.