Line an 8-in. square pan with foil; grease foil with 1 teaspoon butter. With the rest of that butter put it in a pan & melt the butter over medium low, toast the pecans for 5-7 minutes.

In a large heavy saucepan, combine remaining butter, granulated and brown sugars, cream and salt. Bring to a rapid boil over medium heat, stirring constantly. Cook, without stirring, until a candy thermometer reads 234° (soft-ball stage). Remove from heat. Add vanilla to pan (do not stir).

Cool, without stirring, to 110°, about 40 minutes. Beat with a spoon until fudge just begins to thicken. Gradually stir in confectioners' sugar until smooth; add nuts.

Continue stirring until fudge becomes very thick and just begins to lose its sheen. Immediately spread into prepared pan. Let cool and place in fridge for about 2 hours. Using foil, lift fudge out of pan. Cut fudge into 1-in. squares. Store between layers of waxed paper in an airtight container.