Donuts with Custard cream | Without Oven | Nutella

Batter:

130 grams warm milk
35 grams sugar
5 grams instant yeast
1 egg (egg weight including shell total 60 grams)
1 tablespoon cooking oil (10 grams)
300 grams bread flour
1/4 teaspoon salt
15 grams butter

Custard cream:
200 ml milk
15 grams butter
2 egg yolks
35 grams sugar
15 grams cornstarch
1 teaspoon vanilla extract

Nutella