Miso Butter Grilled Cheese | TASTE

Ingredients

• 3 tbsp unsalted butter, at room temperature
• 1 tbsp extra-virgin olive oil
• 1 lg yellow onion, peeled, halved, and thinly sliced
• ½ tsp kosher salt
• 1 tbsp rice vinegar
• 2 tbsp miso butter, at room temperature
• 1 tbsp whole-grain mustard
• 4 slices good-quality sandwich bread
• 1 c grated Gruyère cheese (or ½ cup grated Gruyère with ½ cup grated aged Gouda)
• Cornichon pickles, for serving (optional yet recommended)