Make peanut butter fudge FIRST using the first 4 ingredients. MIX sugar, butter and milk together in a medium/large bowl. Microwave on HIGH for 2 minutes. Beat with a whisk or use a hand mixer to smooth out sugar lumps. ADD peanut butter and microwave for 30 seconds on HIGH. Mix this with a large spoon until creamy. QUICKLY pour this mixture into the prepared pan and spread it out to the edges of the pan Let set for about 30 minutes until firmly set.