In a small bowl, mix together the stout beer of choice (cold) and the simple syrup (also cold) with a whisk. Pour this mixture into the popsicle molds, ice cube trays, silicone molds or small plastic cups. Place into the freeze, making sure the mold/container is level. Freeze for 6 - 12 hours in a 0°F | -17.7°C or below freezer, until completely solid. Since 40% alcohol cannot freeze until 173°F | 78°C, the higher the alcohol content of the beer might change the texture of the finished popsicles.
If you don't want to make popsicles, but like the idea of frozen beer, try the same recipe, but place the mixture into a small casserole pan. Place in the freezer and after 1 hour, using a fork, scrape the mixture. Repeat this scraping every 30 minutes, until the mixture can be formed into an icy pile. This is similar to a Italian Ice called granita.
If traveling with these pops, remember that ice is only 32°F | 0°C and will warm up the pops (being at 0°F | -17.7°C). It is best to use dry ice (-109.3°F | -78.5°C) to transport these pops. Dry Ice can be purchased at most wielding supply stores and some other grocery store locations.
To enhance the chocolate element, add cocoa nibs | chocolate chips | chocolate covered espresso beans to each mold, then top with the popsicle mix
For more ideas and flavor combinations in making Beersicles, check out the blog post.