How to Make It
Preheat oven to 475°F. Grate frozen butter into a large bowl; add flour, and toss well to coat. Chill 15 minutes. Add buttermilk, and stir until a sticky, shaggy dough forms. Coat a 9-inch square metal baking dish liberally with cooking spray. Scrape dough into prepared baking dish, and smooth dough with the back of a spoon. Using a sharp knife,score dough into 16 even squares. Bake in preheated oven until golden brown and cooked through, about 20 minutes. Remove from oven, and brush with melted butter. Let stand 15 minutes.
Meanwhile, whisk together eggs, milk, salt, and pepper in a medium bowl. Coat a 9-inch square metal baking dish with cooking spray, and add egg mixture. Bake at 475°F until eggs are set, 8 to 10 minutes. Remove from oven, and top evenly with cheese slices. Return to oven, and bake at 475°F until cheese melts, 2 to 3 minutes. Remove from oven, and cut into 16 even squares.
Cook sausage patties according to package directions. To assemble the sliders, cut out biscuits, and split using a fork or sharp knife. Place 1 sausage patty and 1 egg-and-cheese square on bottom half of each biscuit, and cover with biscuit tops.