Ingredients:

• 3/4 cup unsalted butter (6 ounces), divided
• 1 cup thinly sliced red onion
• 3 garlic cloves (2 thinly sliced and 1 whole), divided
• 1/4 pound shiitake mushrooms, stems removed and reserved, caps quartered, divided
• 1 medium-size ripe tomato, coarsely chopped
• 1 teaspoon whole black peppercorns
• 1 bay leaf
• 1/3 cup balsamic vinegar
• 1/3 cup water
• Salt
• Freshly ground black pepper
• 3 tablespoons olive oil, divided
• 1 pound fresh spinach
• 2 cups fresh corn kernels
• 1 (1-pound) center-cut salmon fillet, sliced crosswise into 6 strips
• 3 tablespoons finely chopped chives

Cooking Instructions:

1. Cut 6 tablespoons butter into 1/2-inch cubes, and refrigerate until ready to use. Melt 2 tablespoons butter in a medium nonreactive saucepan over medium-low. Add onion, sliced garlic, shiitake stems, tomato, black peppercorns, and bay leaf, and cook until vegetables are soft but not brown, about 12 minutes. Add balsamic vinegar and 1/3 cup water, increase heat to medium-high, and cook, stirring occasionally, until mixture is syrupy, about 4 minutes.
2. Reduce heat to low, and add cubed butter, 2 to 3 pieces at a time, whisking thoroughly between additions. Season sauce with salt and pepper to taste. Pour sauce through a fine wire-mesh strainer into a bowl; discard solids. Keep sauce warm over a double boiler.
3. Spear whole garlic clove with a dinner fork. Heat 2 tablespoons olive oil in a large skillet over high until just beginning to smoke. Add spinach; cook, stirring using fork with garlic clove, until spinach is wilted. Season with salt and pepper to taste; transfer to a colander to drain. Discard garlic clove.
4. Wipe skillet clean with paper towels. Reduce heat to medium, and add 3 tablespoons butter. Add shiitake caps, and cook, stirring, until softened, about 3 minutes. Stir in corn kernels; cook until completely heated through, about 3 minutes. Season with salt and pepper to taste. Transfer to a bowl, and keep warm.
5. Increase heat to high, and add remaining 1 tablespoon butter and remaining 1 tablespoon olive oil to skillet. Season salmon strips with salt and pepper to taste. Add fish to skillet, and cook until browned but barely cooked through, about 3 minutes per side.
6. Divide spinach among 6 plates; surround with corn and shiitakes. Place a salmon strip on top of spinach, and spoon vinegar sauce on fish. Garnish with a sprinkling of chives; serve immediately.