• In a large bowl, combine flour, cornstarch, baking powder, baking soda, and salt, and whisk until well-combined.
  2 cups + 2 Tablespoons all-purpose flour, 1 Tablespoon cornstarch, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
• Use a large spoon to spoon the flour-mixture into the bottom of your mason jar. Tamp down to pack down the flour as much as possible. Use your spoon to create a straight line of flour directly against the glass (so you have nice, even layers) but don’t worry if some of the flour in the middle is uneven or mounded. If you happened to get a lot of flour on the sides of the jar, you can use a paper towel or pastry brush to wipe down the excess flour.
• Add dark brown sugar to the jar and use your spoon to firmly pack over the flour. Again, aim for clean straight edges against the glass.
  ½ cup dark brown sugar¹
• Top with light brown sugar and firmly pack over the dark brown
  ½ cup light brown sugar¹
• Top with granulated sugar.
  ¼ cup granulated sugar
• Top sugar with add-ins, filling to the very top/brim of the mason jar. You want all ingredients to be tightly packed in so they don’t shift during any transportation.
  1-1 ½ cups mix-ins
• Top with mason jar lid and seal tightly. Print off printable instruction tag (find link to printable in the "equipment" section at the top of the recipe) and attach to jar with baker’s twine or ribbon.

Instructions for Gift Recipient:

• Preheat oven to 350F. Let butter cool until no longer warm to the touch. Stir together cooled butter, large egg, and vanilla extract. Add all ingredients from jar and stir well until completely combined (make sure to break up any clumps).

  Drop by rounded 1 ½ Tbsp-sized scoops onto ungreased cookie sheet and bake for 9-11 minutes. Cool on baking sheet and enjoy!
  12 Tablespoons unsalted butter, 1 large egg, 1 teaspoon vanilla extract