Giant Chocolate Peanut Butter Cup

["Spray inside of tart pan ring with nonstick spray. Wrap removable bottom of pan with plastic wrap; gather excess plastic underneath (it should be smooth on top of removable bottom). Set inside ring.", "Heat chocolate in a heatproof bowl set over a saucepan of barely simmering water (bowl should not touch water), stirring, until melted. Remove from heat and, stirring constantly, add oil. Let cool, stirring occasionally, until chocolate mixture firms slightly, about 10 minutes.", "Pour a little less than half of chocolate mixture into prepared pan; reserve remaining chocolate mixture at room temperature. Tilt pan until bottom is evenly coated. Chill until firm, about 15 minutes.", "Meanwhile, puree peanuts, powdered sugar, peanut butter, and salt in a food processor, scraping bowl often, until mixture forms a large mass around the blade that sticks together; do not overprocess or mixture will be too soft and greasy.", "Transfer peanut mixture to a large sheet of wax paper. Press firmly into a disk 1/4"" smaller than diameter of tart pan, about 9 3/4"