Step 1

Place racks in upper and lower thirds of oven; preheat to 350°. Whisk ¾ cup (packed; 160 g) dark brown sugar, ½ cup extra-virgin olive oil, ⅓ cup blue agave nectar, 2 tsp. Diamond Crystal or 1¼ tsp. Morton kosher salt, and 2 tsp. vanilla bean paste or extract in a medium bowl until well combined. Add 1 large egg and whisk to incorporate, then add ¾ tsp. baking soda and whisk vigorously until fully dissolved. Using a sturdy spatula or wooden spoon, stir in 2 cups (250 g) all-purpose flour and 1 cup (200 g) mini chocolate chips until no dry pockets of flour remain.

Step 2

Using a #16 cookie scoop (about ¼ cup), scoop out dough (level dough in scoop) onto 2 parchment-lined rimmed baking sheets (8 cookies per sheet, arranging in columns of 3-2-3 lengthwise), spacing about 1½" apart. (There will be a small amount of cookie dough left over; discard or bake off separately as a cook’s treat.)

Step 3

Bake cookies, rotating baking sheets front to back and top to bottom halfway through, until tops look dry and edges are just beginning to turn golden brown, 8–10 minutes. (To ensure cookies remain soft-ish even when cool, do not overbake.) Let cookies cool on baking sheets until chocolate is no longer melty, about 1 hour. (Or, if you’re in a hurry, let cookies cool on baking sheets 10 minutes, then, using a small offset spatula, transfer all of the cookies to 1 baking sheet, shingling them slightly to fit if needed, and chill in freezer until cold, about 20 minutes.)

Step 4

When ready to assemble, thaw 1½ quarts vanilla ice cream in fridge until pliable (but not melting!), 10–15 minutes.

Step 5

Using a measuring cup, scoop ½ cup ice cream onto bottoms of 8 cookies. Top with remaining 8 cookies, bottoms facing down. Gently press sandwiches together until ice cream is even and at the edges of cookies all the way around.

Step 6

Pour remaining 1 cup (200 g) mini chocolate chips into a shallow bowl. Working one at a time, dip sides of ice cream sandwiches into chocolate chips, pressing gently with your hand so they stick to the ice cream. Tightly wrap each ice cream sandwich in a square (about 10") of plastic wrap. Freeze until ice cream is firm, at least 4 hours and, preferably, up to 12 hours. (Sandwiches can be eaten comfortably straight from the freezer, but feel free to let them sit at room temperature 5 minutes before serving if you’d like.)Do ahead: Cookies can be baked 1 day ahead; store loosely covered at room temperature (they will become noticeably softer; that’s okay). Ice cream sandwiches can be made 2 weeks ahead; keep frozen.