Line an 8” square baking dish with parchment paper.
Heat flour in 10 second increments and stir between until it reaches 160 degrees and set aside (it took mine 4, 10 second increments).
Combine almond bark, sweetened condensed milk, unsalted butter, brown sugar, and salt in a double boiler.
Heat on medium/low heat until smooth.
Once smooth, reduce to low heat and stir in flour until combined.
Remove from heat and stir in vanilla.
Let cool for 3 minutes and add ¼ cup of M&Ms to the batter.
Pour batter into the prepared pan and add the remaining M&Ms to the top.
Let the fudge cool for 6-8 hours or overnight until hard.
Notes
M&Ms do best when they are not refrigerated. So to keep the colors from spreading, let this fudge cool at room temperature.
Best stored at room temperature for 2-3 weeks in an airtight container.