Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a mixing bowl, combine the flour, baking powder, salt, garlic powder, onion powder, and cayenne pepper. Whisk together until well mixed.
Add the cold cubed butter to the flour mixture. Use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.
Stir in the shredded cheddar cheese.
Pour in the milk gradually, mixing until just combined. Do not overmix.
Turn the dough onto a floured surface, and gently knead a few times until it holds together. Roll out the dough to about 1-inch thick.
Use a cookie cutter or round glass to cut out 12 biscuits and place them on the prepared baking sheet.
In another bowl, mix together all the crab filling ingredients until well combined.
Take half of each biscuit, place about 1 tablespoon of the crab filling in the center, and then place the other half on top to cover. Press the edges gently to seal.
In a separate bowl, mix melted butter, garlic powder, and parsley. Brush this mixture over the top of each biscuit.
Bake in the preheated oven for 15-20 minutes or until golden brown.
Remove from the oven and let cool slightly before serving.