Unbelievably Easy Fudge

I found this recipe in a recent issue of Taste of Home, and I couldn't believe it could possibly be any good because it's so simple!  But it actually is rather good.  I've changed it just a teensy bit to make it even easier.  This is not the best fudge recipe I've ever used, but is definitely the fastest and easiest.  If you're daunted by fudge, try this!

Unbelievably Easy Fudge

1 Tbsp butter PLUS a little more for greasing (see instructions)
1 pkg (12 oz) semisweet chocolate chips
1 pkg (11 1/2oz) milk chocolate chips
1 can (14 oz) sweetened condensed milk
1 tsp. vanilla extract

Line an 8" or 9" square baking pan with foil and grease it -- I suggest taking a cold (frozen is great) stick of butter and using it like a crayon to grease the foil.  Set aside.  In a large microwave-safe bowl, melt all the chocolate chips and the 1Tbsp of butter, stirring after 1 minute and then after every 30 seconds until thoroughly melted.  Stir in milk and vanilla until smooth.  Spread into pan and refrigerate until firm.  Lift fudge out of pan, peel off the foil, and cut the fudge into squares.  Store in the fridge.