Step 1 In a small saute pan over low heat, bring 2 cups Madeira to a simmer and cook for 20 to 30 minutes, until it is reduced to one-fourth cup and in a glazey state, watching carefully as it thickens to avoid scorching. Immediately remove the pan from the heat.
Step 2 Quickly whisk in the sherry vinegar. Add the remaining 4 teaspoons Madeira; whisk to combine.
Step 3Transfer the mixture to a medium bowl, whisk in the mustard, grape seed oil, olive oil and pumpkin seed oil. Season with salt and pepper to taste. (You will have dressing left over after assembling the salad; save it for another use.)