Step 1Heat the oven to 375 degrees. Line 3 large cookie sheets with parchment paper.
Step 2Coarsely chop the chocolate into ½-inch chunks, leaving all the flaky bits on the cutting board. Whisk the flour, baking soda and salt in a medium bowl or on a large sheet of parchment or wax paper.
Step 3Beat the butter and both sugars with a stand mixer fitted with the paddle attachment on medium speed, scraping the bowl occasionally, until smooth and creamy but not fluffy, about 3 minutes. With the machine running on medium speed, pour in the cream in a steady stream and beat until smooth. Scrape the bowl, turn the machine to medium-low speed, and add the eggs one at a time then the vanilla. Beat just until smooth and scrape the bowl.
Step 4Turn the machine to low speed and gradually add the flour mixture then the oats. Scrape the bowl, add the walnuts, and mix on low speed until evenly incorporated. You should hear the nuts cracking into smaller pieces as the paddle turns. Scrape in all the chocolate chunks and bits and beat on low speed until well mixed.
Step 5Use a large (3-tablespoon) cookie scoop to drop balls of dough onto a prepared sheet, spacing them 2 inches apart. Bake until golden brown, about 15 minutes. Scoop the remaining dough while the first batch bakes, then bake the remaining sheets, one at a time.
Step 6Cool on the pan on a wire rack. You can wait for them to completely cool or eat them warm. No judgment.
Salted Chocolate Chunk Walnut Oatmeal Cookies: Sprinkle the tops of the dough balls lightly with flaky sea salt, fleur de sel or kosher salt before baking.
Soft and Chewy Chocolate Chunk Cookies: Substitute ¼ cup vegetable oil for 4 tablespoons butter. Beat with the butter and sugar and proceed as above.