1-Line an 8×8 baking dish with parchment: Line an 8×8 baking dish with parchment paper. Be sure to have an overhang on 2 sides to help lift the fudge out of the baking dish. Set it aside.
2-Add the frozen blueberries, sugar, lemon juice,: Add the frozen blueberries, sugar, lemon juice, and cornstarch to a 1 to 2-quart heavy-bottomed saucepan over medium heat. Bring the mixture to a low simmer, whisking frequently to break up the berries until the mixture thickens. This should take about 10 minutes.
3-Place a fine-mesh strainer over a medium-sized: Place a fine-mesh strainer over a medium-sized bowl. Add the blueberry mixture to the strainer. Use a silicone spatula to mash the berry mixture through the strainer. Once you have extracted all the strained, thickened blueberry topping, discard the berry hulls. Cover and chill in the refrigerator for 1 hour.
4-Add the white baking chips and condensed: Add the white baking chips and condensed milk to a large microwave-safe bowl. Microwave for 1 minute, stir and continue heating in 30-second intervals. Continue to stir well after each interval until the chocolate is melted and smooth.
5-Add the blueberry topping to the fudge: Add the blueberry topping to the fudge mixture. Fold 3 to 4 times. Be sure not to overmix the pie filling; you just want a marbled effect.
6-Pour the fudge into the prepared baking: Pour the fudge into the prepared baking dish. Smooth the top of the fudge. Cover and chill in the refrigerator for at least 3-4 hours.
7-Remove the fudge from the pan by: Remove the fudge from the pan by the overhang of parchment paper. Use a large sharp knife to slice the fudge 6 rows x 6 rows giving you 36 pieces of fudge. Keep refrigerated until you are ready to serve.