Some highly rated and quick brown sugar fudge recipes are ones from AllRecipes.com and Epicurious. The recipe from Epicurious requires a candy thermometer and takes about 45 minutes to prepare. The AllRecipes.com fudge uses less ingredients and takes only 15 minutes to prepare.
To make the brown sugar fudge from AllRecipes.com, bring 3 cups brown sugar, 3/4 cup evaporated milk and 1 cup of butter to a boil for 10 minutes. After boiling, remove the mixture from the heat and stir in 2 cups confectioners' sugar. Use an electric mixer to beat the fudge for five minutes. If desired, stir in 1 cup chopped walnuts. Place the fudge into a greased 8-by-8-inch pan and allow to cool before cutting.
For Epicurious' brown sugar fudge, start by mixing together 1/2 cup plus 2 tablespoons evaporated milk, 2 cups brown sugar, 1 1/2 sticks of butter and 1/4 teaspoon salt. Bring the brown sugar mixture to a boil and boil until all sugar dissolves. Lower the heat to a simmer and cook, stirring frequently, until a candy thermometer reads 238 F.
Use an electric mixer to add in 1/2 teaspoon vanilla and 1 3/4 cups confectioners' sugar. Beat the fudge for five minutes, and then spread into an 8-inch baking pan. Refrigerate the fudge until it sets.