For a 22 cm diameter Bundt pan or for eight mini-forms 11 cm diameter by 6 cm high.
1. Stir 125 g flour, the crumbled yeast and milk into a puree in a bowl. Cover and allow to rest in a warm place for 30 minutes. Add the rest of the flour and the sugar, egg yolk, butter, candied orange and lemon peel, raisins, grated orange and lemon peel and salt to the bowl and knead everything to a smooth dough using the bread hook on a hand mixer. Cover with a cloth and allow to rise in a warm spot for about 45 minutes.
2. Brush the Bundt pan or mini-forms with butter and then sprinkle with the almond slivers. Fill each form up to two-thirds full with dough and allow to rise again about 10 - 20 minutes. Bake in a preheated oven at 350 °C for 60 minutes for the big pan and about 30 minutes for the mini forms.
3. Mix the simple syrup with orange liqueur. Cool the Advent gugelkupf on a rack. Then evenly brush with the syrup-orange liqueur mixture. Finally, sprinkle with powdered sugar. Gugelkupf will keep for about 2 weeks when wrapped in saran wrap. They make a perfect gift for the pre-Christmas season.