Line a 6 quart slow cooker with a large piece of parchment paper -- do not skip the parchment paper! Set aside.
Melt the butter. Stir the brown sugar into the melted butter and set aside.
Cut each biscuit (there should be 8 biscuits) into six pieces and separate into individual pieces. Cut each cinnamon roll (there should be 5 cinnamon rolls) into six pieces. Reserve the icing for later.
In a gallon-sized ziploc bag, add the cut biscuits and the cut cinnamon rolls (the cinnamon rolls will fall apart a bit, that okay!) Top with the McCormick® Good Morning Apple Cinnamon French Toast Slow Cooker Breakfast Seasoning Mix and white sugar. Seal the bag and shake until the sugar and seasoning mix coats all of the pieces.
Pour half of the mixture into the bottom of the prepared slow cooker. Pour half of the melted butter + brown sugar mixture on top. Top with the remaining biscuit mixture and finally the remaining butter + brown sugar mixture.
Place 3 sheets of paper towel on top of the slow cooker and add the lid (the lid will hold the paper towels in place).
Cook, covered, on high for 1-2 hours depending on your slow cooker. Check the biscuits every 30 minutes until the biscuits are cooked through. Replace the paper towels at the 1 hour mark.
Optional step: Preheat the oven to High Broil and place the slow cooker insert with the monkey bread inside (only do this if your slow cooker insert is oven safe). Broil, watching carefully, for 2-3 minutes until slightly crisped and golden brown on top. Remove from the oven.
Drizzle the reserved icing (from the cinnamon rolls) over all of the monkey bread. Serve immediately. (You can also use regular syrup to drizzle over the monkey bread!)