Remove the pastry strips from the freezer and let them thaw enough that you can separate them. Remove ten dough sheets from the box, leaving the parchment paper between the dough sheets. Place a damp paper towel or kitchen towel on the sheets to keep the edges from drying out. (See note section for a thawing tip.)
Place the chicken stock into a large pot. Heat on medium-high heat until it comes to a boil.
Peel and cut the carrot into coins. If you make heart-shaped carrots, use a cookie cutter to cut hearts out of the carrot coins. Otherwise, use the carrot rounds as they are. Place the carrots into the chicken stock to cook.
Add the bouillon, salt, pepper, and butter. Stir to dissolve the bouillon.
Use the mini heart cutters to cut out heart shapes from the pastry dough. After you cut a sheet of the hearts, add them one at a time to the boiling chicken stock, stirring lightly after each addition. Continue cutting hearts until you use all of the pastry sheets. Place pastry scraps in a pile under a damp towel to keep them from drying out. Make a ball from the dough scraps and then roll it 1/4-inch thick. Cut heart shapes from the dough and place them into the boiling chicken stock.
Let the pastry cook for 8-12 minutes after adding the last ones. Do not cover the pot. If the water level drops low, add 1-2 cups to bring it back up.
Remove the pot from the heat and add a lid. Let it sit for 30 minutes. The pastry hearts will absorb the liquid during this time and soften. Stir after the 30-minute rest period.
Place the pot on low heat. Add the chicken, whole milk, and evaporated milk. Stir to mix. Heat until hot, but do not boil.