1-First, preheat the oven to 350°F (175°C) and grease a 10×15-inch sheet pan thoroughly with softened butter. This prep work makes sure nothing sticks and your bars come out just right. Gather all your ingredients to keep things smooth and fun.

2-Next, in a large bowl, beat together the softened butter, granulated sugar, and brown sugar until they’re well combined. Add the eggs and 2 teaspoons vanilla extract, mixing everything until it’s smooth. Gradually stir in the flour and baking soda, then fold in the rolled oats until you have a nice dough with no dry spots left.

3-For the filling, heat a medium saucepan over low heat and combine the sweetened condensed milk, chocolate chips, and 1 tablespoon vanilla extract. Stir it continuously until it’s melted and smooth if you’re using walnuts, fold them in now. This step brings that fudgy center to life, so take your time.

4-Now, assemble the bars by pressing three-quarters of the oatmeal dough evenly into the bottom of your greased pan. Pour the warm chocolate fudge filling over the top, spreading it right to the edges. Crumble the remaining quarter of the dough over the filling for that perfect layered effect.

5-Bake everything for 25 minutes, keeping an eye on it so the edges get golden without overdoing the center. Once it’s done, let the bars cool completely in the pan before slicing. This cooling step, which takes about 20 minutes, helps them set up for clean, delicious cuts.