Step 1

Place racks in upper and lower thirds of oven; preheat to 350°. Toast nuts and seeds and oats on a rimmed baking sheet, tossing once, until golden brown, 10–12 minutes. Transfer to a medium bowl; let cool.

Step 2

Meanwhile, mix egg, butter, brown sugar, granulated sugar, vanilla, salt, and baking soda in a large bowl; let sit until nuts are cool (this will make for a chewier cookie).

Step 3

Add dried fruit and chocolate to nut mixture; toss to combine. Give egg mixture a good stir, then stir in flour. Mix in nut mixture, smashing it against the sides of the bowl with a rubber spatula, until combined and mix-ins are evenly coated in dough. (It will look like too many mix-ins, but dough will come together as it chills.) Cover and chill at least 2 hours and up to 3 days.

Step 4

Reheat oven to 350°. Using a ⅓-cup measure or #16 cookie scoop, portion out dough, packing firmly, to make 12 cookies. Divide between 2 parchment-lined baking sheets as you go. Using measuring cup or your hand, press cookies into 2½"-diameter disks about ¾" thick; sprinkle with sea salt.

Step 5

Bake cookies, rotating baking sheets top to bottom and front to back once, until golden brown and no longer wet-looking, 11–13 minutes. Let cool on baking sheets.

Step 6

Do Ahead: Cookies can be made 1 week ahead. Store airtight at room temperature.