Preheat the oven to 200 degrees F. Set a cooling rack over a baking sheet and place in the oven to keep the johnnycakes warm.
For the everything spice: Mix together the poppy seeds, sesame seeds, onion, garlic, salt and pepper in a small bowl and set aside.
For the johnnycakes: Mix together the cornmeal, milk, oil, sugar and egg in a medium bowl. Heat a griddle or skillet over medium-high heat. Add 1 tablespoon oil to the pan once it is hot. Working in batches, drop spoonfuls of the batter onto the pan as you would for pancakes. Sprinkle immediately with some everything spice so it sinks into the cake and adheres. Cook until golden brown around the edges, about 2 minutes. Flip and continue to cook until golden around the edges, about 2 minutes. Remove to the cooling rack in the oven to keep warm and repeat with the remaining batter, adding more oil as necessary.
When ready to serve, divide the johnnycakes among plates. Top each with several slices of gravlax, a spoonful of creme fraiche, some thinly sliced onions and capers and another sprinkle of everything spice. Garnish with some snipped chives.
You can purchase self-rising white cornmeal or make it yourself by combining 1 1/2 cups cornmeal, 6 tablespoons all-purpose flour, 2 tablespoons baking powder and 1 teaspoon salt.