Preheat oven to 350 F. Line an 8-by-8-inch baking pan with aluminum foil, spray with cooking spray; set aside.: The moment you set the oven to 350 F you create a reliable, even heat that bakes the bars through without burning the edges. You should hear the faint hum of the oven as it comes to temperature, and the interior light will glow steady when the heat settles. Lining the 8-by-8-inch baking pan with aluminum foil makes removal and slicing so much easier, and a light spray of cooking spray prevents sticking. A common mistake is skipping foil, which can make the bars difficult to lift from the pan cleanly.
In a large, microwave-safe bowl melt the butter, about 1 minute on high power.: As you melt the unsalted butter in the microwave, watch for it to become fully liquid with golden flecks, and listen for a soft bubbling at the edges. Stir it briefly to distribute heat evenly. If it is too hot when you proceed, it can cook the egg later, so let it settle briefly. Avoid overheating; burnt butter will give an off taste.
Wait momentarily before adding the egg so you don’t scramble it. Add the egg, peanut butter, brown sugar, vanilla, and whisk until smooth.: After allowing the butter to cool slightly, add the egg , SKIPPY Peanut Butter Spread with Salted Caramel , light brown sugar , and vanilla extract . Whisk until the mixture becomes glossy and homogenous. You should feel the batter thicken and see a uniform tan color with no streaks of raw egg or blobs of peanut butter . The aroma will be sweet and toasty, and whisking helps dissolve sugar for a smoother texture. A pitfall is adding the egg too soon into hot butter, which causes curdling.
Add the flour, salt, and stir until just combined, don’t overmix.: Gently fold in the all purpose flour and salt , mixing just until there are no dry patches. You want the batter to hold together without developing gluten, which means stopping when the last veins of flour disappear. The batter should be slightly thick, glossy, and cling to the spatula. Overmixing will yield dense, tough bars, so resist the urge to continue beyond the point of incorporation.
Stir in 1 cup chocolate chips.: When you fold in the main portion of chocolate chips , you ll hear soft clinks as they tumble into the batter and see pockets of dark contrast against the tan dough. This step distributes melty chocolate throughout the bars, giving molten islands after baking. Make sure the chips are evenly dispersed so each bite has chocolate. A common error is dumping chips all at once without folding, which can cluster them unevenly.
Turn batter out into prepared pan, smoothing the top lightly with a spatula.: Scrape the batter into the lined 8-by-8-inch baking pan and smooth the top with a spatula until mostly even. The batter should spread easily but not be runny; you want a uniform layer about three quarters of an inch thick. Smoothing ensures even baking and uniform slices. If you press too hard you may compact the crumb and lose tenderness, so be gentle.
Evenly sprinkle with 2 tablespoons chocolate chips, smoothing them lightly with a spatula or tapping down lightly with your fingertips.: Scatter the remaining chocolate chips on top for a pretty finish, then gently press them in so they adhere. Visually, this creates glossy, melty pockets and ensures the chips do not burn on the surface. The small taps should be gentle; pressing too deeply embeds them and reduces the visual contrast.
Bake for about 20 to 22 minutes, or until done. A toothpick inserted in the center should come out clean, or with a few moist crumbs, but no batter. Bars firm up as they cool. Allow bars to cool in pan for at least 1 hour before drizzling with salted caramel, slicing, and serving. Bars will keep airtight at room temperature for up to 1 week, or in the freezer for up to 6 months.: During baking you ll smell rich butter and caramelized sugar filling the oven, and the surface will turn a warm golden brown. Listen for a low, steady heat hum; the edges may puff a touch and set sooner than the center. Use a toothpick inserted into the center to check doneness, it should come out with a few moist crumbs but not wet batter. The bars continue to set as they rest, so cooling in the 8-by-8-inch baking pan for at least 1 hour is essential before adding the salted caramel sauce . Rushing to slice while warm can make them fall apart, and overbaking will dry them out, so time is everything.