Preheat oven to 400°F/205°C.
In a bowl, beat egg yolks with sugar until mixture is smooth and satiny.
In a separate bowl, beat the egg whites with a mixer until stiff peaks form. Stir the vanilla into the egg yolk mixture, then gently fold in egg whites using a rubber spatula.
Preheat an 8-in. omelette pan over medium heat. When the rim is hot to the touch, add butter. When butter is bubbling briskly, but not burning, add egg mixture.
Place pan in preheated oven for 5 minutes or until mixture is puffed and lightly browned.
Remove soufflé from oven and place sliced strawberries on top. Gently slide soufflé from pan, folding in half as you do so.
Top with fresh whipped cream and slivered almonds, if desired.