Heat the grapeseed oil in a deep frying pan over medium heat.
Meanwhile, wash the sage leaves and then submerge in cold water with ice. Drain the leaves and then lay flat on a paper towel. Pat dry with paper towel and set aside.
In a large mixing bowl, pour in the beer and then slowly whisk in the flour. You may need more or less flour so add it in in small batches. The beer batter should be smooth, with no lumps, and a bit runny. Season with salt and black pepper.
Once the grapeseed oil is hot, submerge each sage leaf in the beer batter and place into the frying pan. Add the sage leaves in small batches to avoid overcrowding. Fry on each side until golden.
Remove from the frying pan and place on a paper towel lined dish. Repeat with remaining sage leaves.
Set aside to soak up the excess oil and then sprinkle with sea salt before enjoying.