Averie Cooks

-1 Preheat oven to 350F, spray oven-safe skillet with cooking spray (mine is a Le Creuset enameled cast iron and I sprayed liberally with Pam for Baking and it released like a charm; if skillet is well-seasoned cast iron, you may wish to butter or grease it slightly); set skillet aside.
-1 In a large microwave-safe bowl, melt the butter, about 1 minute on high power (you may microwave butter to a browned-butter state, which makes this cookie especially delicious, by cooking butter for about 3 to 4 minutes; watch it closely so it doesn't burn.
-1 To the melted butter, add sugar, egg, vanilla, and whisk or stir vigorously to combine, for about 1 minute, slightly fluffing up the batter.
-1 Add the flour, baking soda, salt, and stir until just incorporated. Add the oats and stir to combine.
-1 Pour slightly less than three-quarters of the dough into the skillet, reserving about 1¼ cups (just eyeball it) to be crumbled on at the end; set skillet and large mixing bowl with reserved dough aside.
-1 In a small bowl, combine sweetened condensed milk and peanut butter and stir until smooth. Pour mixture over the dough in the skillet.
-1 Evenly sprinkle the chocolate chips over the top.
-1 Drop tablespoon-sized chunks of the reserved dough into the skillet, dispersing then as uniformly as possible over the surface, which forms the crumble topping.
-1 Bake for about 25 minutes, or until edges begin to barely crisp up and most of the top surface of the cookie has set. The center may not be completely set; this is okay because cookie will continue to cook in the skillet after it's been pulled from the oven, noting that there is a fairly significant carryover cooking effect with cast iron; so don't overbake in the oven because cookie is meant to be very gooey.
-1 Cookie may be served immediately; optionally serve it with ice cream.