Croissant Dough: Mix ingredients together with dough hook attachment of a stand mixer until soft, supple, and elastic dough forms. Rest 30 minutes in an oiled, covered container. On a lightly floured surface, gently roll or pat the dough into a 12” square. Cover tightly with plastic wrap and refrigerate for 30 minutes. While dough is chilling, prepare the butter block.
Place butter between two half sheets of parchment paper and lightly pound with a rolling pin to flatten into a solid 8” square. Chill for 15 minutes until firm but still pliable.
Remove the dough from the refrigerator and roll into a rectangle roughly 12” x 16”. Place the butter block in the center and fold the edges over to seal the butter into the dough. Lightly flour your work surface, and begin rolling the dough gently out into a 12” x 18” rectangle, lifting and fluffing as you go so the dough is not sticking. Fold the dough like a letter in an envelope by folding one end in 2/3 of the way, then the other end over, to create a 3 fold. Wrap the dough tightly in plastic wrap and chill 30 minutes in the refrigerator.
Repeat the rolling and folding process 2 more times total, chilling well between each fold, and rotating the dough 90 degrees each time. Let the dough chill for 1 hour, tightly wrapped, before shaping croissants.
To shape croissants, roll the finished dough out into a ½” thick rectangle, roughly 16” x 12”. Cut the dough in half horizontally, so you have two rectangles 16” x 6”. Cut each strip into 4 triangles 1 ½” wide at the base. Gently stretch each triangle lengthwise and roll up tightly into a croissant. Arrange on two parchment lined sheet pans, spray with pan spray to prevent sticking and cover loosely with plastic wrap. Allow the croissants to proof until doubled in size – about 1 ½ hours. Preheat the oven to 375°F. Just before baking, gently brush the croissants with egg wash (1 egg, beaten well with 1 tsp. water).
Bake until deep golden brown, about 40 minutes. Spread with a generous layer of Bonne Maman Lemon Curd.