Richard Blais's Pimento Jack Cheese Sandwiches

INGREDIENTS

• 8 ounces white pepper jack cheese, coarsely grated
• 1 small poblano pepper, roasted, peeled, seeded, and finely diced
• 1 small jalapeno, seeded and minced
• 1/4 cup
• or good quality store-bought mayonnaise
• 1 tablespoon chopped fresh cilantro
• Grated zest and juice of 1/2 lime
• Kosher salt to taste
• 1/4 cup creme fraiche or sour cream
• 2 tablespoons freshly grated Parmesan
• 1 large egg yolk
• 1 to 2 drops white truffle oil
• 1/2 teaspoon sugar
• Eight 1/2-inch-thick slices brioche or Pullman sandwich white loaf
• 1/2 cup
• 2 tablespoons unsalted butter
• 1/2 cup arugula for serving (optional)