Make a double batch of each flavor of Jello (a double batch using the two boxes of strawberry, and a double batch using the two boxes of blueberry) according to package instructions in two 9×13-inch pans. Refrigerate until completely chilled.

Remove the jello and use a knife to cut each batch into small squares (mine were about 1/2-inch). Carefully remove all squares from the pans, then mix and layer the blocks into a new 9×13-inch pan.

In a separate bowl, sprinkle 2 envelopes unflavored gelatin into 1/2 cup cold water and let it sit for 3 minutes. After the gelatin blooms, add 1 1/2 cup boiling water and stir to dissolve. Stir in the can of condensed milk. Then refrigerate mixture for 20-30 minutes until cooled. Pour cooled milk mixture evenly over jello. If need be, use a toothpick to pop any bubbles that have arisen to the surface (just to make it look smooth). Chill overnight.

Use a knife to cut the jello into squares, or use cookie cutters to cut into fun shapes. Serve.