1. Using a box grater or food processor with a coarse grating disc, grate the potatoes and onion. Transfer the mixture to a clean dish towel and squeeze and wring out as much of the liquid as possible.
2. Working quickly, transfer the mixture to a large bowl. Add the eggs, flour, salt, baking powder and pepper, and mix until the flour is absorbed.
3. In a medium heavy-bottomed pan over medium-high heat, pour in about ¼ inch of the oil. Once the oil is hot (a drop of batter placed in the pan should sizzle), use a heaping tablespoon to drop the batter into the hot pan, cooking in batches. Use a spatula to flatten and shape the drops into discs. When the edges of the latkes are brown and crispy, about 5 minutes, flip. Cook until the second side is deeply browned, about another 5 minutes.
4. Transfer the latkes to a paper towel-lined plate to drain and top with Petite Ash Brie slices while still warm.
5. Repeat with the remaining batter.
6. Top with fruit jam of your liking and a sprig or two of fresh rosemary. Enjoy!