In a large pot over medium heat, combine the milk, water, sugar, salt, and butter. Cook until the butter melts.
2. Step
Add the flour, all at once, and using a flexible spatula, stir until combined. Continue to mix until the dough pulls away from the sides of the pan and forms into a ball. Remove the pot from the heat and let cool for 2-3 minutes.
3. Step
Preheat oven to 425°F (220°C). Line a baking sheet with parchment paper.
4. Step
Mix in the eggs, one by one, only adding the next once the previous is fully incorporated into the dough.
5. Step
Transfer the dough to a piping bag fitted with a large round tip or a zip-top bag with a corner snipped off.
6. Step
Pipe the dough straight down onto the prepared baking sheet in 1-inch (2 cm) circles, leaving 1 inch (2 cm) of space between each one. You may need to use another baking sheet.
7. Step
Use a wet finger to press down any peaks.
8. Step
Bake for 25-30 minutes, until puffed and golden brown.
9. Step
Let the puffs cool completely on a wire rack.
10. Step
Make the filling: In a large bowl, use an electric hand mixer on high speed to beat the heavy cream until soft peaks form.
11. Step
Pour in the condensed milk and continue to beat until stiff peaks form. Add the food coloring and beat to incorporate.
12. Step
Transfer the cream to a piping bag with a pointed round tip or a zip-top bag with a corner snipped off.
13. Step
Add the white chocolate to a medium microwave-safe bowl and microwave until melted, stirring every 30 seconds, about 2 minutes total.
14. Step
Use a bamboo skewer to poke a hole in the top of each puff, then pipe in the pink or blue cream, filling each puff about ⅔ of the way.
15. Step
Dip the tops of the filled cream puffs in the white chocolate and decorate with sprinkles, if desired.
