Instructions: In a large, preferably nonstick, saute pan over medium heat, cook onions slowly in butter until onions are caramelized (takes 7-10 minutes).

Sprinkle with brown sugar and cook, stirring constantly, until golden brown. Remove from heat.

In the large bowl of an electric mixer, combine caramelized onions, mustard, vinegar, porter, herbs, garlic, pepper and salt. Mix on low speed until well blended.

Increase speed to medium and pour oil slowly into the bowl in a thin stream. Mix until all the oil is incorporated and the dressing is well blended. Stir in the mustard seed.

Serve immediately over spinach salad.

Makes 2 cups, about 10 (3-tablespoon) servings.

Note: To clarify butter, melt in microwave, let sit for a couple of minutes until the white solids come to the top, then skim off and discard.

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