In a small bowl, blend together the cream cheese, mascarpone, chives, and salt. Spread the mixture on 4 slices of the bread and top with the remaining bread. Spread 1 1/2 teaspoons of the butter on each side of each sandwich.
Heat a griddle or large skillet over medium-high heat. Add 2 sandwiches and cook until golden brown, 1 1/2 to 2 minutes per side. Remove and repeat with the remaining sandwiches. Cut each sandwich into 2 triangles. Serve immediately.
Yield: 4 servings