Puree strawberries. Press through a fine mesh strainer into a clean bowl.

In a small saucepan set over medium heat, melt butter. Remove from pan from heat. Whisk in sugar, cornstarch, strawberry puree and lemon juice. Whisk in yolks one at a time, whisking until fully combined. Return to heat. Continue whisking occasionally until thickened. Remove from heat. 

Press curd through a fine mesh strainer to remove any impurities. 

Transfer to desired storage container. Cover and cool to room temperature. Use immediately or chill until ready use.