In a large bowl, beat butter and confectioners' sugar with an electric mixer until creamy, 5 to 6 minutes. Add vanilla and salt beating to combine. In another bowl, whisk together flour and cornstarch. Add flour mixture to butter mixture, beating to combine. Shape dough into a disk, and cover with plastic wrap. Refrigerate for 2 hours. Preheat oven to 350º. Line baking sheets with parchment paper. Set aside. Scoop dough into 1-inch mounds. Roll mounds into balls: place on prepared pans, spacing 2 inches apart. Using a wet fingertip, press to make two small indentations in the middle of each cookie to create a heart shape. Spoon approximately 1/2 teaspoon Raven's Nest Strawberry Jalapeño Jam into each indentation. Bake until lightly browned, 12 to 15 minutes. Let cool on pans for 5 minutes. Remove from pans, and let cool completely on wire racks. Store in an airtight container for up to 5 days.