Mix flour, salt and sugar in a large bowl. Add eggs and 65 g butter in flakes. Warm the milk. Crumble yeast into it and dissolve it while stirring. Pour onto the flour mixture and knead into a smooth dough using the dough hooks of the hand mixer. Cover with cling film and chill overnight.
Knead the yeast dough on a floured work surface with your hands and put it back into the bowl. Cover and leave to rise in a warm place for about 1 hour.
Whisk 250 g of soft butter until light and creamy with the whisk of the hand mixer. Stir in 3 teaspoons Fleur de Sel. Divide the dough into two equally sized pieces and roll out each into a strand (approx. 75 cm long) on a floured work surface. Roll out each strand of dough 14-16 cm wide. Spread the dough strands with 40 g of the salted butter and 4 tbsp. strawberry jam each. Leave one edge (2-3 cm) free. Roll up each strand of dough from the long side to a snail. Twist the ends on one side each. Cut approx. 2/3 of each strand of dough in the middle. Fold the cut surfaces slightly apart. Lay the cut strands alternately on top of each other to create the pattern of a cord. Twist the ends together. Twist the beginning and end of the braid together to form a wreath.
Place the yeast plait in a spring tray (approx. 32 cm Ø). Place a preserving jar (approx. 8 cm Ø, approx. 8 cm high) in the middle. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 35-40 minutes. After 25-30 minutes of baking time cover the wreath with aluminium foil. Remove the wreath from the oven, sprinkle with 1 teaspoon Fleur de Sel and allow to cool. Arrange the strawberry and yeast wreath. Serve with the rest of the salted butter.