If you're looking for a meeting place or a good stop around ½ or halfway between Asse and Puurs, you can try Londerzeel, Belgium, which is about 19 minutes northeast of Asse, or about 19 minutes south of Puurs.
About ⅓ or a third of the way, you can stop at Meise, Belgium. This is about 11 minutes east of Asse.
If you drive straight through without stopping at all, the total distance is 34 km. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 38 minutes.