Peel the potatoes skin and very good to mash into a puree, to avoid lumps, it is better to do it in blender. No weights, but I took a 3.5 potatoes, a little smaller than average size. Then, when stretched, measured, get a Cup ready puree (200 ml).

Margarine is very good to mix with sugar. Then add the eggs, one at a time, beating well after each, about 1 - 1,5 minute.

Then add the zest and lemon juice, mix well.

Add the puree, mix until smooth.

Semolina mixed with baking powder, ginger and vanilla. Add the semolina mixture to the batter, mix until smooth. The dough was very airy and light, like whipped cream.

Molds well lubricated with oil, if there is a paper insert, it is better to use them. Put the dough in three fourth of the height. A few berries to put on top and push them into the dough so that they almost completely drowned. But you can put the batter, then the berries, and the berries again the dough. The berries I had frozen and NOT thawed. 6 stuff was done with raspberries, the second 6 with black currants. Bake in a preheated oven at 180 degrees for 30 - 35 minutes. The finished muffins to stand in tins for 7 - 10 minutes, then gently pull out the hot dough incredibly soft and crumbly, it is likely to get only half of the muffin. If desired, sprinkle with powdered sugar.