To make the syrup melt the butter over medium heat in a medium size pot. When the butter begins to foam remove it from the heat and slowly add the brown sugar, buttermilk, baking soda and vanilla. Whisk until smooth, return the pot to the heat and bring to a boil. Allow the syrup to thicken slightly, about 2-3 minutes. Remove from the heat and set aside.
In a large bowl add the buttermilk ,eggs, vanilla and melted butter. Whisk to combine. Add the flour, baking powder and salt. Fold the dry ingredients into the wet ingredients until just combined.
Line an 8x8 inch square baking dish with parchment paper. In a large, heavy-bottomed pot add 1 stick butter, melt butter over medium heat. Add the marshmallows and turn off the heat. Stir the marshmallows around until completely melted, about five minutes. If the marshmallows are not fully melting turn the heat back on to low and stir until smooth and melted. Grease 1/3 cup measuring spoon and scoop out 1/3 cup of marshmallows. Stir the 1/3 cup of melted marshmallows into the pancake batter.
Now add the Rice Krispies to the pot with the remaining melted marshmallows and coat them completely in marshmallows. Press the mixture into the prepared baking dish (the treats will not completely fill the square pan). You just want one even layer of Rice Krispie treats. Tear away a few bits and pieces of the Rice Krispie treats and stir them into the pancake batter.
Heat a skillet or griddle over medium heat and grease well with butter or cooking spray. Using a 1/4 cup measure, spoon batter into rounds. Tear a few more bits of Rice Krispies away from the square and place them on top of the pancakes, cook until bubbles form on top, about 2-3 minutes. Flip and cook for another minute or two more. Repeat with remaining batter.
Serve the pancakes warm, drizzled with the butter syrup and a square of Rice Krispie treats if desired. Enjoy!
*Syrup adapted from [Two Peas and Their Pod | http://www.twopeasandtheirpod.com/brown-butter-buttermilk-syrup/] and [All Recipes | http://allrecipes.com/recipe/buttermilk-syrup/]