This is the one my Mother used for years, from the Hershey's can.
It is on the Hershey's site.
Is it close to what you're looking for?

RICH COCOA FUDGE

3 cups sugar
2/3 cup HERSHEY'S Cocoa or HERSHEY'S Dutch Processed Cocoa
1/8 teaspoon salt
1-1/2 cups milk
1/4 cup (1/2 stick) butter
1 teaspoon vanilla extract

1. Line 8-or 9-inch square pan with foil, extending foil over edges of pan. Butter foil.

2. In heavy 4-quart saucepan, stir together sugar, cocoa and salt; stir in milk. Cook over medium
heat, stirring constantly, until mixture comes to full rolling boil. Boil, without stirring, until mixture
reaches 234°F on candy thermometer or until small amount of mixture dropped into very cold
water, forms a soft ball which flattens when removed from water. (Bulb of candy thermometer
should not rest on bottom of saucepan.)

3. Remove from heat. Add butter and vanilla. DO NOT STIR.
Cool at room temperature to 110°F (lukewarm).

4. Beat with wooden spoon until fudge thickens and just begins to lose some of its gloss.
Quickly spread into prepared pan; cool completely. Cut into squares. Store in tightly
covered container at room temperature.
About 36 pieces or 1-3/4 pounds.

NOTE: For best results, do not double this recipe.

VARIATIONS: NUTTY RICH COCOA FUDGE:
Beat cooked fudge as directed. Immediately stir in 1 cup chopped almonds, pecans or walnuts
and spread quickly into prepared pan.

MARSHMALLOW-NUT COCOA FUDGE: Increase cocoa to 3/4 cup. Cook fudge as directed.
Add 1 cup marshmallow creme with butter and vanilla. DO NOT STIR.
Cool to 110°F (lukewarm). Beat 8 minutes; stir in 1 cup chopped nuts.
Pour into prepared pan. (Fudge does not set until poured into pan.)

HIGH ALTITUDE DIRECTIONS: -- Increase milk to 1-2/3 cups -- Use soft ball cold water test
for doneness OR Test and read thermometer in boiling water, subtract difference from 212°F.
Then subtract that number from 234°F. This is the soft ball temperature for your altitude and
thermometer.

Prep Time: 25 min.
Start to Finish: 3 Hrs. 20 min.

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Developed and Tested by the Hershey Kitchens
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