Melt the milk and semisweet chips in a double boiler (see Note). If using the microwave, stop the microwave and give the chips a stir every 15 to 20 seconds until they are melted.
Place the noodles in a large bowl. Pour the melted chocolate over and stir to combine. Add half of the S’more Baking Chips Mix, and stir and toss until everything is evenly combined.
Drop the mixture by tablespoons onto the prepared baking sheet. Use your fingers to tuck in a few extra bits of marshmallow, graham crackers, and chocolate squares around the tops of the haystacks, pushing them in slightly so they will stick. Allow to set (in warmer months, this is best done in the fridge, though let them sit at room temperature for several minutes before serving).
Notes
If you don’t have a double boiler, you can make one by nestling a metal or heatproof glass bowl over a pot with a bit of water in the bottom — bring the water to a boil, and stir the chips frequently until they melt.If you can't find the S'mores baking mix at your grocery store, substitute an equal amount of a combo of mini marshmallows, additional milk chocolate chips, and graham crackers. Break the graham crackers up into tiny pieces before adding them.