Whisk sugar and water together in a small saucepan until dissolved. Bring to a simmer. Add the cocoa and salt, whisking to blend. Remove from the heat and add chocolate and stir until melted and smooth. Cool to room temperature until thickened slightly, or refrigerate until cold (reheat before serving).
Make the crepes
Combine the buttermilk, water, flours, eggs, butter, sugar and salt in a blender until smooth, about 30 seconds. Scrape down the container to incorporate any flour sticking to the side and blend for a few more seconds to mix. Cover the container (or transfer to a bowl) and chill at least 1 hour or overnight.
Combine the strawberries, sugar and olive oil and let stand 10 minutes or so while making the crepes.
Heat an 8-inch nonstick pan over medium-high heat until a drop of water sizzles instantly on the surface.
Brush the pan with 2 or 3 tablespoons butter and add enough batter to thinly coat the bottom of the pan - I use a small ladle. Immediately tilt and swirl pan to make an even circle of batter.
Cook the crepe until the bottom is set and light golden – you can shake the pan a little to see if it slides. If it does, it’s about ready to flip. Turn the crepe over gently with your fingers or small spatula and cook the other side for another minute or two.
The first crepe is usually a practice one, but congratulations if yours comes out perfectly! Repeat the process with the rest of the batter, stacking crepes and layering with wax or parchment paper as you go.
Serve crepes topped with strawberries and warm chocolate sauce.