Start by preheating your oven to 350°F. While the oven heats up, grease your skillet well. Use a little butter or baking spray. This stops the brownies from sticking to the pan.

Place the butter and chopped chocolates in a glass bowl. Microwave them in 30-second bursts. Stir well after each burst until smooth. Let the mixture cool down for a few minutes.

In a separate large bowl, whisk the eggs and sugar. Use a hand mixer for about two minutes. The mixture should look pale and fluffy. This adds air and creates a light texture.

Slowly pour the cooled chocolate into the egg mixture. Add the vanilla extract now too. Stir gently with a spatula. Make sure everything is well combined and looks dark and glossy.

Sift the flour, baking powder, and salt together. Add them to the wet ingredients. Fold them in gently until you see no white streaks. Do not overmix the batter at this stage.

Fold in the semi-sweet chocolate chips. These chips create the "molten" pockets of chocolate. They stay soft even after the brownies bake. This makes every single bite extra gooey.

Pour the thick batter into your prepared skillet. Smooth the top with your spatula. Bake for about 30 minutes. The center should still be a little bit wobbly when finished.

Remove the skillet from the oven carefully. Let it sit for 5 to 10 minutes. This allows the center to set slightly. Serve it warm directly from the skillet for the best taste.