Preheat the oven to 400˚F
Carefully peel peaches. Slice.
Combine flour, sugar, baking powder, salt, mace in a mixing bowl and stir well with a whisk.
Add the cold butter pieces and incorporate to blend well until it becomes fine crumbs.
In a small mixing bowl, whisk milk and egg well. Pour the milk mixture over the flour mixture. Mix with a fork just until it becomes wet.
Grease a 9-inch spring form pan and spread the batter on the bottom of the pan.
Arrange the peach slices on top. Bake in the oven for 15 minutes.
Meanwhile, make the custard cream. In a small mixing bowl, combine 1/4 cups of cream with flour and whisk together to get rid of big lumps. Add the rest of the cream, sugar, egg, vanilla, and salt. whisk well to mix.
Take the cake out of the oven and pour the cream mixture on top. Put the cake back in the oven and reduce the heat to 350˚Continue to bake for 35-40 minutes.
When the cake top is puffed, and the edges are deep golden and starting to separate from the pan, the cake is done. Cool in the pan for 15 minutes, then remove it from the pan and let it cool completely.