Here are a few mustard recipes, all from Henley's 20th century Home & Workshop Formulas, Recipes and Processes, 1913 edition. I've tried a few of them, and they are excellent. The main issue with home-made mustard is that it could be difficult to grind the seeds finely enough, but even a coarser consistency will work great.
Some of the batches are enormous, so you should probably scale them.
Kirschner Wine Mustard
30 quarts freshly pressed grape juice
5 lbs sugar
3 large hoseradishes
2½ dm cardamom
2½ dm nutmeg
4½ dm cloves
1 oz cinnamon
1 oz ginger
6 lbs brown mustard
9 lbs yellow mustard
Reduce the grape juice to half the quantity over slow fire. Dissolve the sugar in the juice. Pour the syrup through a colander covered with muslin and layered with the horseradishes cut into very thin slices. To the colate add the rest, very finely ground.
Düsseldorf Mustard
10 oz brown mustard
48 oz yellow mustard
96 oz boiling water
64 oz wine vinegar
5 dm cinnamon
15 dm cloves
64 oz sugar
64 oz good white wine
Grind and mix.
German Table Mustard
8 oz bay leaves
5 dm cinnamon
2 dm cardamom
64 oz sugar
96 oz wine vinegar
10 oz brown mustard
48 oz yellow mustard
Grind and mix.
Moutarde de Jésuittes
12 sardels (anchovies)
280 capers
3 pints wine vinegar
4 oz brown mustard
8 oz yellow mustard
Crush sardels and capers. Stir into the boiling vinegar. Add the finely ground mustard.
Tarragon Mustard
40 parts brown mustard
20 parts yellow mustard
6 parts vinegar
6 parts tarragon vinegar
Boil the finely ground mustard in the vinegar and add the tarragon vinegar.
Tarragon Mustard, sharp
Follow the recipe above. To every 100 lbs of the above, add 21 oz white pepper, 5 oz chili and 2½ oz cloves. Let stand for two weeks, then strain.
Moutarde aux Épices
10 lbs yellow mustard
40 lbs brown mustard
1 lb tarragon
5 oz basil
12 dm bay leaves
3 oz white pepper
12 dm cloves
2 dm mace
1 gallon vinegar
Macerate the ground spices in the vinegar to exhaustion, then strain through a muslin. Add the finely ground mustard.
Ravigotte Mustard
2 parts parsley
2 parts chervil
2 parts chives
1 part cloves
1 part garlic
1 part thyme
1 part tarragon
8 parts salt
4 parts olive oil
128 parts white wine vinegar
Yellow mustard, sufficient
The spices must be fresh. Cut or bruise the plants and spices and macerate in the vinegar for three weeks. Strain the liquid and add the salt. Add olive oil and finely ground mustard to desired consistency.
Notes:
Where the amount of salt in the recipes is not specified, it is to be added to taste.
The 8 oz bay leaves in German Table Mustard above seems strangely much. It probably applies to fresh bay leaves, but even so seems way too much. Use your judgement.
1 gallon = 3.79 litres
1 quart = 0.95 litre
1 pint = 0.47 litre
1 lb (pound) = 454 grams
1 oz (ounce) = 28.3 gram
1 dm (drachm) = 1.78 gram