- Vegetable oil cooking spray
- 27 store-bought chocolate wafer cookies (6 ounces)
- 1 tablespoon plus 1 1/2 teaspoons sugar
- Table salt
- 1 stick plus 2 tablespoons unsalted butter
- 1 pound bittersweet or semisweet chocolate, chopped
- 1 can (14 ounces) sweetened condensed milk
- 1/4 cup whole milk
- 1/2 teaspoon pure vanilla extract
- 1/2 cup toasted and finely chopped walnuts
- Coarse salt, preferably fleur de sel
- Preheat oven to 400 degrees. Coat a 9-by-13-inch baking dish with cooking spray, and line with parchment, leaving a 2-inch overhang on long sides. Spray parchment.
- Pulse wafers in a food processor until finely ground, and transfer to a bowl. Add sugar and a pinch of table salt. Melt 6 tablespoons butter, and stir into crumbs. Press into bottom of dish. Bake for 10 minutes.
- Heat chocolate, condensed milk, whole milk, remaining 4 tablespoons butter, and a pinch of table salt in a double boiler or a heatproof bowl set over a pan of simmering water, stirring, until melted. Stir in vanilla.
- Pour chocolate mixture over baked cookie layer, smoothing top with an offset spatula. Sprinkle walnuts and coarse salt over top, pressing slightly to adhere. Refrigerate until firm, about 2 hours.
- Remove fudge from dish using parchment to lift, and transfer to a cutting board; remove parchment. Trim edges of fudge with a sharp knife, and cut crosswise into six 2-inch-wide strips. Cut each strip crosswise into 3 equal bars, then cut each bar in half on the diagonal to form 36 triangles.
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