Cut the pumpkin into small cubes. Place in a pan and cover with water, 2 tablespoons of sugar, and bring to a boil. Cook until the squash is soft. Drain well and mash finely.
Let the pumpkin puree cool.
Mix the flour with 60 grams (approximately 1/4 cup) of sugar and salt in a bowl. Make a well in the center. Crumble the yeast into a small bowl with a pinch of sugar. Pour 100 ml (approximately 1/2 cup) of lukewarm milk into the bowl. Let sit for 3-4 minutes. Add the pumpkin puree. Pour the milk mixture into the well. Add the egg yolks, butter, and remaining milk. Knead into a smooth elastic dough. The dough should be soft. Cover the dough and let rise in a warm, not drafty area for about 1 hour. Knead again vigorously.
Heat the oil in a pot or in a deep fryer to 180°C (approximately 350°F). Roll the dough out thinly and cut into donuts. Fry in portions in the hot oil until golden brown. Drain on absorbent paper and allow to cool briefly. Sprinkle with powdered sugar and serve immediately. Serve with fresh berries and a fruit sauce to taste.