Place the brie in the freezer for at least an hour.

Mix flour, salt, yeast, water, and oil in a bowl.

Mix until the dough becomes pliable.

Knead the dough on a floured surface until smooth.

Place the dough in an oiled bowl and cover with oiled plastic wrap.

Let the dough rise until it has doubled in size.

Preheat the oven to 375 degrees Fahrenheit.

Brush olive oil over a cast iron skillet or a thick-bottomed cookie sheet.

Place the dough on the skillet and use your fingers to roll it out.

Remove the brie from the freezer and remove all wrappers.

Spread deli mustard over the cheese.

Wrap the dough around the cheese.

Place the egg in a small bowl and add a dash of water.

Mix with a whisk or a fork.

Brush the loaf with the egg mixture.

Sprinkle poppy seeds over the loaf.

Bake for 15-25 minutes.

Allow to cool slightly before serving warm.