Wrap the outer bottom of a 7-inch (18 cm) springform pan with 2 layers of foil, going at least halfway up the sides. This will prevent water from leaking into the pan when placed in the water bath. Then, line the inside bottom of the pan with parchment paper.
Press half of the cookie dough evenly against the bottom and about ⅓ of the way up the sides of the pan. Pour in the cheesecake batter.
Place the springform pan in an 11-inch (27-cm) round pan or roasting pan. Fill the larger pan with hot water until it reaches halfway up the sides of the springform, being careful not to splash any onto the cheesecake. Carefully transfer the pan to the oven and bake for 45–55 minutes. The center of the cheesecake should still jiggle slightly when you shake the pan.
Turn off the oven and leave the cheesecake inside for 1 hour to cool. Carefully remove the cheesecake from the water bath and let cool at room temperature for another hour, then transfer to the refrigerator to chill for at least 4 hours, or overnight.
Reduce the oven temperature to 325°F (160°C). Line a baking sheet with parchment paper.
Using a #30 (1-ounce) scoop, scoop the remaining cookie dough onto the prepared baking sheet. You should get about 18 cookies. (Alternatively, wrap the remaining dough in plastic wrap and store in an airtight container in the refrigerator for up to 2 weeks, or in the freezer for up to 2 months.)
Bake the cookies for 12–15 minutes, until the edges brown slightly. Remove from the oven and immediately sprinkle the cookies with flaky sea salt. Let cool on the baking sheets for 10–15 minutes, then transfer to a wire rack to cool completely. Cut 2–3 of the cookies in half, then crush 2–3 more for topping the cheesecake. Reserve the remaining cookies for another use.
Make the toffee sauce: In a medium pot, combine the brown sugar, cream, and butter. Cook over medium-low heat for 3–4 minutes, until starting to thicken. Add the vanilla and flaky salt and cook for another minute, until the salt dissolves.
Pour the sauce into a heatproof jar, cover, and let cool at room temperature. The sauce will keep in an airtight container in the refrigerator for up to 2 weeks.
Once the cheesecake has chilled, use a knife or offset spatula to loosen the cheesecake around the sides of the pan, then release the springform. Transfer the cheesecake to a serving platter.
Top the cheesecake with the toffee sauce, halved cookies, crushed cookies, and mini chocolate chips.