converting the recipe - pressure cooker Streusel Coffee Cake

Any idea how to convert this recipe to not use the strange baking mix?

https://recipes.instantpot.com/recipe/streusel-coffee-cake/

Ingredients
2 1/3cups all-purpose baking mix (such as Bisquick)divided
1/2cup packed brown sugar divided
1/2tsp ground cinnamon
4tbsp cold butter divided
1large egg
2/3cup Water

Instructions
Grease a 7-inch nonstick fluted tube pan (such as a Bundt or kugelhopf).
In a small bowl, combine 1/3 cup baking mix, 1/3 cup brown sugar and cinnamon. Using a pastry blender or two knives, cut in 2 tbsp butter until crumbly. Sprinkle half the streusel mixture in bottom of prepared pan.
In a medium bowl, combine the remaining baking mix and brown sugar. Cut in the remaining butter until crumbly.
In a measuring cup or bowl, whisk egg and water. Add to dry ingredients and stir until just combined.
Pour half the batter over streusel mixture in pan. Sprinkle with the remaining streusel. Top with the remaining batter.
Add 1 cup hot water to the inner pot and place the steam rack in the pot. Place the pan on the rack.
Close and lock the lid and turn the steam release handle to Sealing. Set your Instant Pot to Pressure Cook on High for 25 minutes.
When the cooking time is done, press Cancel and let stand, covered, for 10 minutes, then turn the steam release handle to Venting. When the float valve drops down, remove the lid. A tester inserted in the center should come out clean. (If more cooking time is needed, continue pressure cooking on High for 3 minutes, then quickly release the pressure.)

I saw a lot of recipes like that to replace the Bisquick mix, but the problem is that this is the only recipe that I'm going to make with that mix so I don't want to mix up 6+ cups of mix only to use about 2 cups of it.  

Surely there is some way to convert the recipe instead of making up a mix?  

I am sure there's a calculator somewhere for this but based on my baking experience, I would use the same amount of flour the recipe calls for, 2 tsp baking powder, 1/2 tsp baking soda and 1/2 tsp of salt (I'm not a fan of salt, so up to 1tsp if you prefer saltier taste).

I think this would get you the slight bite taste of the biscuit mix, but if you don't want that, back off a bit on the powder/soda.

Good luck and fingers crossed, R.

I agree with what Sonja suggested.

Here is one I found on google using one cup of flour:

Homemade Bisquick Substitute Recipe

   1 cup all-purpose flour.
   1½ teaspoons baking powder.
   ½ teaspoon salt.
   1 tablespoon vegetable oil (or melted unsalted butter, shortening)

https://eugeniekitchen.com › bisquick-substitute