Carefully add 1 cup flour to hot milk, stirring until smooth.
When cool, crumble yeast into the mixture.
Let rise for half an hour.
Add salt to eggyolks and beat until thick and lemon colored.
Add eggs, sugar, and rum to the sponge and mix.
Add remaining flour and knead until dough no longer sticks to the hand.
Add butter and knead until thoroughly blended.
Let rise until double in bulk.
Punch down and let rise again.
Use glass to cut dough into doughnut shapes.
Fill dough with preserves.
Place on lightly floured surface and let rise again.
Fry in hot fat, turning only once.