Lime Semifreddo with Pretzel Crust Recipe

Name: Lime Semifreddo with Pretzel Crust Recipe
Ingredients: 1 cup pretzel crumbs (about 2 cups of small pretzel sticks); 5 tablespoons unsalted butter, melted; 2 tablespoons light brown sugar; 1 (14-ounce) can sweetened condensed milk; 1/2 cup lime juice; 2 teaspoons finely grated lime zest; 1 cup sugar; 1/4 cup water; 2 tablespoons light corn syrup; 4 large egg whites, at room temperature; 1/4 teaspoon salt