01 -
Mix the flours, sugar and yeast in a mixer bowl. Add butter cubes, eggs, lukewarm milk, vanilla and salt. Knead with dough hook on low speed for 10 minutes until smooth and slightly tacky. Shape into a ball with a few quick kneads.
02 -
Place dough in a lightly oiled bowl, cover with plastic wrap, and let rise for 2-3 hours until tripled in size.
03 -
Knock out air from the risen dough, knead briefly, then roll to 1/2 inch thickness. Cut into 3.5-inch rounds using a cookie cutter. Place on parchment paper, cover loosely, and let prove again for 1-1.5 hours until tripled in size.
04 -
Whisk egg yolks, sugar, vanilla, and lemon zest in a bowl. Add cornstarch and mix well. Heat milk until hot, cool for 1 minute, then slowly pour into egg mixture while whisking. Return to pan and heat gently while stirring constantly until very thick (10-15 minutes). Transfer to a bowl, cover surface directly with plastic wrap, and cool completely.
05 -
Heat oil to 170°C/337°F in a deep pan. Cut parchment into squares with one doughnut per square. Carefully drop doughnuts into hot oil (with parchment), then immediately remove parchment with tongs. Fry in batches for 2 minutes per side. Drain on paper towels for 2 minutes, then roll in sugar while still warm.
06 -
Once cooled, make a small incision in the side of each bomboloni with a knife. Pipe pastry cream into the center of each doughnut. Serve immediately for best results or store in containers for 1-2 days.