(I know using vegan recipes is the best option, but I'd love to bake this cake)

I have never replaced egg in a recipe and I don't know enough baking chemistry to know which egg replacement option to use. I'd be very thankful for your help :)

Ingredients: (the recipe is for 4 times the amount of dough/creme but I only want to make 1 cake, that's where the weird fractions come from)

• 100g sugar

• 3/4 egg

• 62.5g margarine

• 100g sour creme (vegan cream cheese?)

• 1/2 tbsp baker's ammonia

• 1/2 tbsp oil

• 1/8 tsp salt

• 325g flour

Creme:

• 250ml milk (soy milk)

• 1 tbsp lour

• 2 eggs

• 100g sugar

• 150g butter

• 100g powdered sugar

For the cream you have to whisk the egg whites until stiff (aquafaba baking powder?), the yolk gets mixed with sugar, what could i use for the yolk?

For the creme, I have to put the egg parts into boiling milk, boil and let it cool.