Preheat oven to 425°F.
Combine yeast and 1/4 teaspoon sugar to warm water. Stir to dissolve; set aside for 5 minutes or until foamy.
In large bowl, whisk together flour, baking powder, baking soda, remaining sugar and Old Bay Seasoning.
Using a pastry blender, cut cold butter into dry ingredients until butter is the size of peas and evenly distributed throughout the flour mixture. This may take 3 to 4 minutes, and will help ensure biscuits don't spread out while baking.
Using a dough whisk or wooden spoon, stir in buttermilk and yeast mixture to flour/butter mixture until just combined. Stir in cheddar cheese and parsley. Do not over mix. Using hands, mix dough until it just comes together into a large ball. See note2.
Prepare pan: Generously spray baking sheet with nonstick spray or line with parchment paper. Place a second baking sheet underneath to prevent bottoms of biscuits from getting too brown.
Measure 1/4 cup (about 65g) of dough, form into a mini patty shape that is thick and flat on top. Transfer to prepared baking sheet. Repeat with remaining dough. Space each biscuit 2 inches apart.
Mix melted butter and 1/4 teaspoon Old Bay Seasoning.
Bake biscuits 10 minutes. Brush with melted butter mixture and sprinkle with flaked salt. Bake 2 additional minutes, or until light golden brown. Serve warm.