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1
Position rack in the center of the oven, preheat to 350AF.
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2
Line an 8-inch-square baking pan with the foil, allowing it to overhang on two opposing sides.
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3
Spray with cooking spray or grease with butter.
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4
Sift together the flour, powdered sugar and cocoa powder into a small bowl.
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5
Mix the 3 ounces semi-sweet chocolate chips and oil in a heavy medium saucepan.
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6
Put over the lowest heat, stirring, until just melted and smooth, do not overheat the chocolate..
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7
Remove from the heat and stir in sugar, corn syrup mixture, vanilla and salt until the sugar dissolves.
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8
Slowly stir in egg until smoothly incorporated.
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9
Gently stir in the dry ingredients.
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10
Fold in the walnuts (if needed) and the remaining 2 1/2 ounces mini chocolate chips just until well mixed.
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11
Transfer the batter into the pan, spreading evenly.
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12
Bake until almost firm in the center and a wooden stick inserted comes out with some moist batter clinging to it, 22 to 26minutes.
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13
Allow to cool completely in a pan on a wire rack, about 2 1/2 to 3 hours.
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14
Using the overhanging foil as handles, slowly lift the brownie squares from the pan.
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15
Remove the foil from the bottom, set the square right-side up on a cutting board.
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16
Using a large, sharp knife, trim off any dry edges.
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17
Mark and then cut the square crosswise into fifths and lengthwise into fourths.
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18
Wipe the blade with a damp cloth between cuts.
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19
Serve or store at an air-tight container.
