Adapted from David Leite in the New York Times Food section. Inspired by Thalia Ho.
Line a baking sheet with a silicone mat or parchment paper
In a heavy skillet or saucepan, combine the sugar, corn syrup, and water, and cook over medium high heat, without stirring, until the mixture begins to slightly color.
Swirl the pan (don't stir), and continue cooking the sugar mixture, swirling occasionally, until the caramel is an even, deep amber color. This will only take a few minutes.
Remove this caramel from the heat, use a silicone or rubber spatula to quickly stir in the chopped nuts and a pinch of salt, and then turn the mixture out onto the lined baking sheet, using the spatula to spread it in an even layer.
Allow the praline to cool and harden, and then transfer it to a cutting boar and chop it into small-ish pieces with a sharp knife.
Sift the three flours, baking soda, and baking powder together into a medium bowl, and whisk in the salt. Set aside.
In an electric stand mixer fitted with the paddle attachment, cream the butter, brown sugar, and granulated sugar until light and fluffy. Add the eggs, one at a time, beating well after each addition. Mix in the vanilla.
With the mixer on low speed, add the flour mixture, and mix until just combined. (This should only take 10 seconds or so.)
Add 1 lb. of chocolate discs or feves and the chopped hazelnut praline, and mix on low speed to slightly distribute the additions. Then, turn off and remove the bowl from the mixer, and use a sturdy silicone or rubber spatula to finish incorporating the chocolate pieces and hazelnut praline.
Cover the bowl with plastic wrap and refrigerate for at least 24 hours, preferably 36 hours, and up to 72 hours.
When you are ready to bake the cookies, line two baking sheets with parchment paper or silicone mats, and preheat the oven to 350 F.
Using an ice cream scooper or large spoon, scoop 6-8 mounds of dough--about 70 grams each--onto the first cookie sheet. If you are pro-chocolate-puddle (and, really, who isn't?), nestle an extra chocolate feve or two into the top of each mound of dough.
Repeat with the second cookie sheet.
Place one cookie sheet in the oven, and bake the cookies for approximately 18-20 minutes. Halfway through the baking time, open the oven and (with oven-mitt-protected hands!) bang the baking sheet against the oven rack. Close the oven, and then, one minute later, bang the pan again. Repeat this pan-banging 2 more times (for a total of four times), at one minute intervals.
When the cookies are golden brown and the chocolate is molten, remove the cookies from the oven. Sprinkle flaky sea salt over the molten puddles of chocolate, and let the cookies cool on the pan for 5 minutes before transferring them to a wire rack to cool completely.
Meanwhile, bake the second sheet of cookies, following the process above.
When both sheets are baked, you can repeat the process with the remaining cookie dough, leave the remaining dough in the fridge and bake another batch or two over the next couple of days, or scoop out and freeze the remaining dough to bake cookies at a later date.