Preheat the oven to 400°F. Line a baking sheet with parchment and set aside.
Carefully cut off and reserve the top of the brie. Place the brie round on one unrolled pie crust. Sprinkle the brie round with the garlic, chives, and rosemary. Place the top of the brie over the garlic mixture.
Lay the second pie crust over the brie. Use your hand to gently press the edges against the brie and smooth up the sides. Make sure not to press down on the outer edges of the crust– just focus around the brie.
Cut even-sized strips all around the brie, like a sun, making about 18 cuts in total. Place one cocktail sausage at the outer leftmost corner of one of the strips at a slight angle. Roll it inward to wrap in the pie dough and press the edges to seal. Continue all the way around until the first layer of strips are all wrapped around cocktail sausages. You may have to move the wrapped sausages gently in the process in order to fit others– that’s okay.
Continue to wrap the bottom layer of strips around cocktail sausages and push the top layer above them in the process. Brush generously with egg yolk, and sprinkle with sesame seeds and poppy seeds, if desired.
Carefully transfer or slide the wrapped brie to the lined baking sheet. Bake the brie until the pastry is deep golden-brown, about 30 to 40 minutes.
Allow to cool 5 to 10 minutes to allow the cheese to firm up slightly. Cut the top off of the baked brie and serve warm.