Better Than Nutella (Chocolate-Hazelnut Spread)

Name: Better Than Nutella (Chocolate-Hazelnut Spread)
Yield: Makes about 4 cups
Ingredients: 2 cups (heaping) hazelnuts, preferably skinned (about 10 ounces); 1/4 cup sugar; 1 pound semisweet or bittersweet chocolate, coarsely chopped; 1/2 cup (1 stick) unsalted butter, cut into 1-inch pieces, room temperature; 1 cup heavy cream; 3/4 teaspoon kosher salt; Four clean 8-ounce jars