To skin the hazelnuts, bring a cup of water to a boil in a medium saucepan, add 1/2 a tsp of baking soda and the nuts, and boil for 3 to 5 minutes, until the water turns black. To test if the skins have loosened sufficiently, drop a nut into a bowl of cold water and rub lightly against the skin. if the skin just slides off,the nuts are ready to go. Turn the nuts into a colander and run cold water over them. Slip off the skins, toss the nuts into a towel, pat dry, and use as required.
Position the rack in the center of the oven and preheat the oven to 350 deg F(180 deg C). Brush a light coating of butter over the insides of 8 mini-loaf pans, each 4 1/4 by 2 1/2 by 2 inches. Dust the inside of the pan with a little flour and tap out the excess.
Place the hazelnuts and 1 tbsp of sugar in a mixer or processor and just process until the nuts are finely ground, taking care not to overdo this or you'll end up with hazelnut butter. Its absolutely fine if its not totally ground. Whisk or stir together the ground hazelnuts, flour, baking powder, and salt just to combine; set aside.
In a separate bowl, add the almond extract to the creame fraiche and stir to blend and loosen the creme fraiche; reserve.
Put the butter and the remaining sugar in the bowl of a paddle attachment, or use a hand-held mixer, and beat on a medium-high speed until the mixture is smooth and creamy, scarping down the sides of the bowl with a rubber spatula as needed. The butter and sugar must be beaten until they are light, fluffy, and pale, so dont rush it- the process can take 3 to 4 minutes with a heavy-duty mixer or 6 to 8 minutes with a hand-held mixer.
Reduce the speed to medium and add the eggs one at a time, beating well after each addition.
Divide the batter evenly among the prepared pans, filling the pans between half and two-thirds full, then give each pan a couple of raps against the countertop to settle the batter.
Place the pans in the oven and bake for about 30 minutes, or until a toothpick inserted in the center of a cake comes out clean. (Test a couple of the cakes to be certain.) Remove from the oven, turn them out of their pans onto a rack and cool.
The loaves can be served warm or at room temperature. Serve one loaf to a person, either slicing the loaves in half diagonally or cutting them into thin slices.
Storage: The cakes can be kept covered at room temperature for about 2 days or wrapped airtight and frozen for a month. Thaw still wrapped, at room temperature.