Strawberry ice cream topping can be made up to 2 days in advance. Store in an air-tight container in the refrigerator. To double or triple the recipe, simmer strawberry juice/lemon juice/sugar/cornstarch mixture for 2 to 5 minutes longer, and shape shortcake dough into 2 or 3 balls before baking (don't try to make 1 giant doubled shortcake). For buttermilk substitutions, freezer instructions, and recipe ideas for using up leftover buttermilk, check out this post.