In a medium bowl, stir together 1 cup natural peanut butter, 1/2 cup powdered sugar, and 1 teaspoon kosher salt with a spatula until well-mixed (it should resemble soft cookie dough at this point). Add 2 teaspoons cold water, and mix again. The water will make the dough wet at first, then as soon as it begins to get mixed in, the dough-like texture should stiffen to where it's almost kind of dry and crumbly-looking.
Transfer the peanut butter "dough" to a sheet of parchment paper on a clean countertop and top it with a second sheet of parchment. Roll the dough out until it's somewhere between 1/2 to 1cm (1/4 -1/2 inch). Roll the dough thinner if you like a higher chocolate-peanut butter ratio, thicker if you like them more peanut buttery (note that the thicker you make the dough, the fewer pieces you will get).
Use whatever cookie cutter shape you like to cut the dough into shapes (aim for a cookie cutter that's about 5-8cm (2-3 inches). Alternatively, if you don't have cookie cutters, you can skip the above step and simply roll the peanut butter dough into balls or even free-hand shape them into egg shapes.
Transfer the shaped peanut butter pieces onto a parchment-lined baking sheet, and put the sheet into the freezer until the dough is relatively solid (about 30 minutes). Note that it's possible to coat them with chocolate immediately, but it will be easier and you will get better results if the shapes are at least somewhat frozen.
If you're using a milk chocolate bar, chop it into pieces and place the chopped chocolate in a small, microwave-safe bowl. Microwave the chocolate in 30-second intervals until it's melted (my chocolate took a total of 60 seconds to melt).
Using a fork (a larger fork is easier), lift one of the pieces of peanut butter filling into the bowl of chocolate. Quickly flip the filling over and lift it out, ensuring that the whole thing is covered with chocolate. With the candy sitting on top of the tines of the fork, gently rap the fork against the edge of the bowl to remove excess chocolate.
Gently slide the peanut butter egg off the fork with a second utensil and place it back on the parchment-lined baking sheet. Repeat with the remaining pieces of peanut butter filling until they've all been dipped in chocolate. If the chocolate begins to solidify, microwave it again in 15-20-second intervals as needed.
Transfer the baking sheet to the fridge for the chocolate to set. Store the eggs in an airtight container or zipper bag in the fridge to prevent the chocolate from melting, especially if it's warm.
Notes
The peanut butter I used had only one ingredient - peanuts. If yours contains added sugar or salt, your results may differ from mine. Check the ingredient list if you're unsure.If you use a different kind of salt and you're measuring by volume vs weight, you may need to adjust the amount of salt in your recipe. If you're using table salt, reduce the amount to 1/2 teaspoon. If you use Morton (or Windsor) Kosher salt, use 3/4 teaspoon.