In the bowl of a stand mixer combine flour, sugar, and yeast
Add the eggs, milk, and liqueur, then knead for 3–4 minutes
Gradually add the soft butter and salt, then continue kneading for 8–10 minutes until a smooth, elastic dough forms
Cover and let rise for 1–1.5 hours until doubled in volume
Degas the dough, divide into 65–70 g pieces, shape into balls, place each on a square of parchment paper, and proof for another hour until doubled
Heat oil to 165–170°C
Fry each donut about 3 minutes per side until golden brown
Let cool completely at room temperature
Place all the cream ingredients in a saucepan and whisk well
Cook over medium heat while whisking constantly until thickened
Remove from the heat, add the butter, and mix until smooth
Cover with plastic wrap directly on the surface and refrigerate
In a saucepan heat the sugar, water, and glucose until a golden caramel forms
Pour onto a tray and spread into a thin layer
Let cool completely until hardened
Break into pieces, place in a small saucepan, and gently heat until fully melted
When the caramel is hot and fluid, dip the top of each donut and shake lightly to create a thin layer
Transfer the pastry cream to a piping bag with a tip and fill each donut from the bottom
